Add missing parentheses to fix MISRA C-2012 Rule 12.1.

Also, the result of a comparison is an essentially boolean value, it
isn't needed to return 1 or 0 depending on it.

Also, fix header guards (MISRA C-2012 Rule 21.1).

Change-Id: I90c0bcdeb2787c1ca659fc9a981808ece7958de3
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>