arm: lib: add __gnu_thumb1_case_si

The assembly for __gnu_thumb1_case_si was taken from upstream gcc and adapted
as width suffix was removed for the add instruction [1].

Signed-off-by: Francis Laniel <francis.laniel@amarulasolutions.com>
Tested-by: Tony Dinh <mibodhi@gmail.com>
[1] https://github.com/gcc-mirror/gcc/blob/4f181f9c7ee3efc509d185fdfda33be9018f1611/libgcc/config/arm/lib1funcs.S#L2156
Acked-by: Pali Rohár <pali@kernel.org>
Acked-by:  Tony Dinh <mibodhi@gmail.com>
1 file changed