trusty: add return value test for munmap() calls am: 29464e917d am: 00f0e3f2f7

Original change: https://android-review.googlesource.com/c/trusty/app/confirmationui/+/3239335

Change-Id: I08ae6df48ad2194d24cd2895553202bfc1dc15b7
Signed-off-by: Automerger Merge Worker <[email protected]>