-Wlogical-op prevents common errors with using numerical constants where
a boolean one is expected as well as when the operands of a logical
operator are the same. While these are perfectly valid behavior, they
can be a sign that something is slightly off.

This patch adds this warning to gcc and it's closest equivalent to
clang, while also fixing any warnings that enabling them causes.

Change-Id: Iabadfc1e6ee0c44eef6685a23b0aed8abef8ce89
Signed-off-by: Justin Chadwell <justin.chadwell@arm.com>