arm: Declare symbols as .type function

[dg0yt]

While revising the vcpkg port, I ran into this error pattern when building a test project for arm-neon-android (NDK r27c, static linkage) during a find_package(BLAS) in CMake:

ld.lld: error: /vcpkg/installed/arm-neon-android/debug/lib/libopenblas.a(sgemm_nn.c.o):(function sgemm_nn: .text.sgemm_nn+0x232): branch and link relocation: R_ARM_THM_CALL to non STT_FUNC symbol: sgemm_otcopy interworking not performed; consider using directive '.type sgemm_otcopy, %function' to give symbol type STT_FUNC if interworking between ARM and Thumb is required; level3.c:332 (/vcpkg/buildtrees/openblas/src/v0.3.28-a14d95ad12.clean/driver/level3/level3.c:332)

The solution is adapted from common_arm64.h etc.

[martin-frbg]

Thanks - I'm not sure if there are (still) any real-world applications of iOS on ARMv6, but it certainly doesn't hurt to support them.