fconf: Fix misra issues

MISRA C-2012 Rule 20.7:
Macro parameter expands into an expression without being wrapped by parentheses.

MISRA C-2012 Rule 12.1:
Missing explicit parentheses on sub-expression.

MISRA C-2012 Rule 18.4:
Essential type of the left hand operand is not the same as that of the right
operand.

Include does not provide any needed symbols.

Change-Id: Ie1c6451cfbc8f519146c28b2cf15c50b1f36adc8
Signed-off-by: Louis Mayencourt <louis.mayencourt@arm.com>