fatfs: Added full support for multiple fs volume prefixes
fatfs: Added full support for multiple fs volume prefixes

This is only an issue when multiple fatfss are used simultaneously.
Repeated use of a single fatfs instance (even with different storages)
do not show this issue.

Full support requires path prefixes being applied for every function
that takes a path. Note: this is only required filesystems after the
first mounted filesystem. The first filesystem has no penalty.

pradeep-gr/mbed-os5-onsemi,infinnovation/mbed-os,ryankurte/mbed-os,HeadsUpDisplayInc/mbed,betzw/mbed-os,svogl/mbed-os,betzw/mbed-os,fahhem/mbed-os,mbedmicro/mbed,NXPmicro/mbed,YarivCol/mbed-os,adamgreen/mbed,betzw/mbed-os,CalSol/mbed,andcor02/mbed-os,adamgreen/mbed,nRFMesh/mbed-os,nRFMesh/mbed-os,mbedmicro/mbed,Archcady/mbed-os,fahhem/mbed-os,ryankurte/mbed-os,pradeep-gr/mbed-os5-onsemi,adamgreen/mbed,adamgreen/mbed,svogl/mbed-os,HeadsUpDisplayInc/mbed,pradeep-gr/mbed-os5-onsemi,kjbracey-arm/mbed,mazimkhan/mbed-os,NXPmicro/mbed,Archcady/mbed-os,karsev/mbed-os,karsev/mbed-os,Archcady/mbed-os,HeadsUpDisplayInc/mbed,mazimkhan/mbed-os,infinnovation/mbed-os,svogl/mbed-os,catiedev/mbed-os,infinnovation/mbed-os,c1728p9/mbed-os,kjbracey-arm/mbed,catiedev/mbed-os,andcor02/mbed-os,YarivCol/mbed-os,YarivCol/mbed-os,kjbracey-arm/mbed,mbedmicro/mbed,fahhem/mbed-os,monkiineko/mbed-os,adamgreen/mbed,andcor02/mbed-os,bcostm/mbed-os,c1728p9/mbed-os,c1728p9/mbed-os,catiedev/mbed-os,nRFMesh/mbed-os,CalSol/mbed,c1728p9/mbed-os,ryankurte/mbed-os,Archcady/mbed-os,andcor02/mbed-os,bcostm/mbed-os,NXPmicro/mbed,c1728p9/mbed-os,monkiineko/mbed-os,CalSol/mbed,ryankurte/mbed-os,nRFMesh/mbed-os,HeadsUpDisplayInc/mbed,svogl/mbed-os,bcostm/mbed-os,bcostm/mbed-os,fahhem/mbed-os,mbedmicro/mbed,pradeep-gr/mbed-os5-onsemi,svogl/mbed-os,nRFMesh/mbed-os,nRFMesh/mbed-os,YarivCol/mbed-os,betzw/mbed-os,ryankurte/mbed-os,svogl/mbed-os,CalSol/mbed,bcostm/mbed-os,mbedmicro/mbed,karsev/mbed-os,monkiineko/mbed-os,betzw/mbed-os,karsev/mbed-os,kjbracey-arm/mbed,karsev/mbed-os,fahhem/mbed-os,Archcady/mbed-os,mazimkhan/mbed-os,monkiineko/mbed-os,andcor02/mbed-os,infinnovation/mbed-os,pradeep-gr/mbed-os5-onsemi,YarivCol/mbed-os,betzw/mbed-os,NXPmicro/mbed,adamgreen/mbed,ryankurte/mbed-os,monkiineko/mbed-os,mazimkhan/mbed-os,NXPmicro/mbed,andcor02/mbed-os,bcostm/mbed-os,infinnovation/mbed-os,mazimkhan/mbed-os,monkiineko/mbed-os,YarivCol/mbed-os,fahhem/mbed-os,karsev/mbed-os,HeadsUpDisplayInc/mbed,catiedev/mbed-os,catiedev/mbed-os,HeadsUpDisplayInc/mbed,CalSol/mbed,catiedev/mbed-os,NXPmicro/mbed,pradeep-gr/mbed-os5-onsemi,Archcady/mbed-os,infinnovation/mbed-os,CalSol/mbed,c1728p9/mbed-os,mazimkhan/mbed-os