trusty: Extend smc function and move to arch specific asm file

Extend trusty smc function to pass 8 registers in both directions. Move
to separate assembly files so r7 can be used (in thumb mode r7 got
corrupted by the inline assembly even though it was specified as an
output).

Signed-off-by: Arve Hjønnevåg <arve@android.com>
Bug: 128698138
Change-Id: I76fc5169182d687981fc6ce854f6489e055cfd01