msm: scm-boot: update scm boot data structure

The scm call to set the secondary boot address uses
a non-explicitly-sized type in the buffer structure
passed on to thesecure world. Fix this by using
explicitly sized types; otherwise the size of the
structure fields and the structure will vary between
32 and 64 bit platforms.

Change-Id: I339342dafb79f9ec05c152a7e12479bb094b79f6
Signed-off-by: Abhimanyu Kapur <abhimany@codeaurora.org>