common_arm.h, common_mips.h: get rid of .func directives

common_arm.h, common_mips.h: get rid of .func directives

.func/.endfunc are gcc/gas-specific directives for generating stabs
debug information (and nothing more). This is near-useless now because
DWARF is commonly used, and not implemented in Clang. Hence building
OpenBLAS with Clang fails, and there is no sane way to detect GCC vs.
anything else with preprocessor definitions.

Hence, just remove these directives.