trusty: Fix implicit int conversions and add some missing truncations

Use explicit casts to truncate 64 bit registers to 32 bit arguments for
ffa functions that are defined to take 32 bit arguments. Some of these
where already truncated implicitly when calling the function that
implements the specific ffa call, but some were incorrectly using the
full 64 bit register value.

Bug: 185886035
Change-Id: I308304fea41fd217dfcb666694a7aba18364382d
1 file changed