README: Fix IMAGE_FSTYPES example
README: Fix IMAGE_FSTYPES example

The SD image is always created with the extension "rpi-sdimg" and this cannot be
changed by editing IMAGE_FSTYPES.

Change-Id: I7336e8c698f13fba14ef9cc9bf6c0b262bf261e5
Signed-off-by: Paul Barker <a027184a55211cd23e3f3094f1fdc728df5e0500@paulbarker.me.uk>

agherzan/meta-raspberrypi,agherzan/meta-raspberrypi,agherzan/meta-raspberrypi,git4vijay/meta-raspberrypi,gbraad/yocto-meta-raspi,leon-anavi/meta-raspberrypi,MCherifiOSS/s-osg-meta-raspberrypi,git4vijay/meta-raspberrypi,pficheux/meta-raspberrypi,gbraad/yocto-meta-raspi,ThomArmax/meta-raspberrypi,VCTLabs/meta-raspberrypi,agherzan/meta-raspberrypi,LocutusOfBorg/meta-raspberrypi,git4vijay/meta-raspberrypi2,pficheux/meta-raspberrypi,d21d3q/meta-raspberrypi,schnitzeltony/meta-raspi-light,rofehr/meta-raspberrypi,wware/meta-raspberrypi,agherzan/meta-raspberrypi,gbraad/yocto-meta-raspi,thiagoss/meta-raspberrypi,kovrov/meta-raspberrypi,VCTLabs/meta-raspberrypi,schnitzeltony/meta-raspberrypi,ThomArmax/meta-raspberrypi,git4vijay/meta-raspberrypi,hwh7/meta-raspberrypi,MCherifiOSS/meta-raspberrypi,schnitzeltony/meta-raspberrypi,toolmmy/meta-raspberrypi,thiagoss/meta-raspberrypi,kraj/meta-raspberrypi,thiagoss/meta-raspberrypi,leon-anavi/meta-raspberrypi-testsand,leon-anavi/meta-raspberrypi-testsand,hwh7/meta-raspberrypi,gbraad/yocto-meta-raspi,ajlennon/meta-raspberrypi,schnitzeltony/meta-raspberrypi,wware/meta-raspberrypi,git4vijay/meta-raspberrypi2,ThomArmax/meta-raspberrypi,kovrov/meta-raspberrypi,leon-anavi/meta-raspberrypi,ajlennon/meta-raspberrypi,rfbsoft/polievanie_meta-raspberrypi,git4vijay/meta-raspberrypi2,MCherifiOSS/meta-raspberrypi,hwh7/meta-raspberrypi,toolmmy/meta-raspberrypi,LocutusOfBorg/meta-raspberrypi,rofehr/meta-raspberrypi,ajlennon/meta-raspberrypi,d21d3q/meta-raspberrypi,MCherifiOSS/s-osg-meta-raspberrypi,amirna2/meta-raspberry,agherzan/meta-raspberrypi,schnitzeltony/meta-raspi-light,kraj/meta-raspberrypi,toolmmy/meta-raspberrypi,cocoonlife/meta-raspberrypi,d21d3q/meta-raspberrypi,VCTLabs/meta-raspberrypi,rofehr/meta-raspberrypi,amirna2/meta-raspberry,rfbsoft/polievanie_meta-raspberrypi,rofehr/meta-raspberrypi,MCherifiOSS/s-osg-meta-raspberrypi,git4vijay/meta-raspberrypi2,d21d3q/meta-raspberrypi,leon-anavi/meta-raspberrypi,hwh7/meta-raspberrypi,LocutusOfBorg/meta-raspberrypi,leon-anavi/meta-raspberrypi-testsand,cocoonlife/meta-raspberrypi,leon-anavi/meta-raspberrypi-testsand,thiagoss/meta-raspberrypi,ajlennon/meta-raspberrypi,VCTLabs/meta-raspberrypi,kraj/meta-raspberrypi,rfbsoft/polievanie_meta-raspberrypi,ThomArmax/meta-raspberrypi,rfbsoft/polievanie_meta-raspberrypi,pficheux/meta-raspberrypi,amirna2/meta-raspberry,LocutusOfBorg/meta-raspberrypi,toolmmy/meta-raspberrypi,kovrov/meta-raspberrypi,git4vijay/meta-raspberrypi,pficheux/meta-raspberrypi,MCherifiOSS/s-osg-meta-raspberrypi