spd: trusty : fix defects flagged by MISRA scan

spd: trusty : fix defects flagged by MISRA scan

Main Fixes:

Use int32_t replace int [Rule 4.6]

Added explicit casts (e.g. 0U) to integers in order for them to be
  compatible with whatever operation they're used in [Rule 10.1]

Force operands of an operator to the same type category [Rule 10.4]

Fixed if statement conditional to be essentially boolean [Rule 14.4]

Voided non c-library functions whose return types are not used
[Rule 17.7]

Change-Id: I98caa330c371757eb2dfb9438448cb99115ed907
Signed-off-by: Anthony Zhou <anzhou@nvidia.com>