modpost: rename R_ARM_THM_CALL to R_ARM_THM_PC22

/usr/include/elf.h, which originates from the glibc/musl, defines
R_ARM_THM_PC22 instead of R_ARM_THM_CALL.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>