arm: lib: Fix uldivmod.S build on Thumb2

arm: lib: Fix uldivmod.S build on Thumb2

This assembler source won't build in Thumb2 mode, so fix it adding
the necessary Thumb2 conditional macros from unified.h .

This patch also defines CONFIG_THUMB2_KERNEL and CONFIG_ARM_ASM_UNIFIED
which is necessary for correct build of these files both in ARM and
Thumb mode, just like Linux does.

Signed-off-by: Marek Vasut <[email protected]>
Cc: Albert Aribaud <[email protected]>
Cc: Masahiro Yamada <[email protected]>
Cc: Simon Glass <[email protected]>
Cc: Tom Rini <[email protected]>
Reviewed-by: Tom Rini <[email protected]>