firmware: qcom_scm: Rename macros and structures

Rename legacy-specific structures and macros with legacy prefix; rename
smccc-specific structures and macros with smccc prefix.

Change-Id: I501e38377f063e2ee27c1bc4b0a17426bb6e556e
Signed-off-by: Elliot Berman <eberman@codeaurora.org>