msm: scm: Add scm_call_noalloc and helper macros

Currently, scm_call internally calls kmalloc() to allocate a command
buffer structure. This prevents scm_call from working before kmalloc
structures are initialized or during atomic contexts. Allow clients
to pass in a pre-allocated buffer for scm_call to be used for internal
structures.

Change-Id: Id09500c8c696298228aefdcc2a61953e654677c9
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>