Mark OPENSSL_armcap_P as hidden in asm files.

Without this, the linker says:
  (sha512-armv4.o): requires unsupported dynamic reloc R_ARM_REL32; recompile with -fPIC

This is (I believe) a very misleading error message. The R_ARM_REL32
relocation type is the correct type for position independent code. But
unless the target symbol is hidden then the linker doesn't know that
it's not going to be overridden by a different ELF module.

Change-Id: I9bb5f6b5f85c8de1ad5b6426cf27826976ce8248
6 files changed