This change ensures that Sansa Connect bootloader.bin will fit in its flash
partition.
Fix _flash_sizem calculation, division was not working properly because
FLASHSIZE included subtraction and defined value was not in parenthesis.
Prior to this change _flash_sizem was 0x00800000, now it is correctly set
to 4 in case of Sansa Connect and 8 in case of other TMS320DM320 players.
This significantly improves boot time as cache is now enabled only for
real flash memory region.
Change-Id: If3e50a3075c840dcb69dfafe5bba608a0acd2bf8