trusty: add couple non-secure memory related helper routines

trusty_encode_page_info - encodes page physical address, memory
type and other attributes into architecture specific structure
that can be parsed by secure side.

trusty_call32_mem_buf - can be used by drivers to make
specified smc call with physicaly contigues memory buffer as
an argument. Memory buffer info in retrieved by trusty_encode_page_info
and along with buffer size is encoded into series of 32-bit
smc call parameters.

Change-Id: Iae155c0eff0bb6269be1abbe53ee42f27a1c23f5
Signed-off-by: Michael Ryleev <gmar@google.com>