ANDROID: fips140: change linker script guard

Currently, the linker script's support for merging module's section is
guarded by either CONFIG_LTO_CLANG or CONFIG_CRYPTO_FIPS140_MOD. This
functionally is also needed by additional fips140 modules built out of
tree. So, have an explicit config (CRYPTO_FIPS140_MERGE_MOD_SECTIONS)
that can be selected by the various fips140 modules without having to
depend on and enabling CONFIG_CRYPTO_FIPS140_MOD.

Bug: 281657135
Change-Id: I2af727813151ba839a95696bc847e2a841a7175a
Signed-off-by: Konstantin Vyshetsky <vkon@google.com>