refactor(lib/smc): Move feature bit definitions to RMI header

This patch moves some of the defines mandated by RMM specification to
the smc-rmi.h so as to keep all specification related defines in a
single header.

Signed-off-by: Yousuf A <yousuf.sait@arm.com>
Signed-off-by: Soby Mathew <soby.mathew@arm.com>
Change-Id: I0e2a1b031f4668c6bc969674711b49ac66841e9c