msm: implement ARCH_RANDOM

Currently, the software random number generator is not intialized
until relatively late in the boot process. Software that relies on
random numbers early will not be reliable. Entropy sources are
available early but not early enough for some use cases which means
that moving the software random number generation earlier is not an
option. As an alternate solution, implement the functions associated
with CONFIG_ARCH_RANDOM. These functions currently make a call into
trustzone to get reliable random numbers. The functions are disabled
once the regular random number generator is sufficiently reliable.

Change-Id: If40cfcb96b091fa26a28047c10a902287b26f6c1
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>