Fix regression in 'update_kernel.sh' for Tegra2 boards.
Fix regression in 'update_kernel.sh' for Tegra2 boards.

This 'update_kernel.sh' script gratuitiously broke on ARM targets
because the bootloader file has been changed to 'bootloader.bin' from
its previous name.

TEST=Used the script with a small kernel change to my Arthur board.
BUG=none

Change-Id: I146f08256543ffe2c4c52995625b26a1b3f28318
Reviewed-on: http://gerrit.chromium.org/gerrit/1989
Reviewed-by: Olof Johansson <13dc431ca3b0f062f888def8f8ec4662ec608f7d@chromium.org>
Reviewed-by: Taylor Hutt <39a9c928d8a3a00d7fd484a843cc4ccfc80af42c@chromium.org>
Tested-by: Taylor Hutt <39a9c928d8a3a00d7fd484a843cc4ccfc80af42c@chromium.org>

mjg59/scripts,BugRoger/scripts,crawford/scripts,mischief/scripts,coreos/scripts,BugRoger/scripts,zhang0137/scripts,marineam/coreos-scripts,sigma/coreos-scripts,glevand/coreos--scripts,crawford/scripts,fivethreeo/scripts,gtank/scripts,BugRoger/scripts,mjg59/scripts,bcwaldon/coreos-scripts,gtank/scripts,mischief/scripts,gtank/scripts,andrejro/coreos--scripts,vmware/coreos-scripts,mjg59/scripts,zhang0137/scripts,nicescale/scripts,smilart/scripts,vmware/coreos-scripts,marineam/coreos-scripts,fivethreeo/scripts,trnubo/scripts,mischief/scripts,sigma/coreos-scripts,crawford/scripts,endocode/scripts,fivethreeo/scripts,andrejro/coreos--scripts,smilart/scripts,endocode/scripts,sigma/coreos-scripts,vmware/coreos-scripts,nicescale/scripts,smilart/scripts,glevand/coreos--scripts,andrejro/coreos--scripts,trnubo/scripts,coreos/scripts,bcwaldon/coreos-scripts,nicescale/scripts,zhang0137/scripts,marineam/coreos-scripts,endocode/scripts,bcwaldon/coreos-scripts,trnubo/scripts