cipher/Makefile.am: add '-fcoverage-*' to instrumentation munging

* cipher/Makefile.am: Remove '-fcoverage-*' flag for mixed asm/C
i386+amd64 implementations.

Combination '-fprofile-instr-generate -fcoverage-mapping' was causing
build error as former was removed by munging and latter requires thay.

• Signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>