Enable -Wlogical-op always

-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>
diff --git a/drivers/mentor/i2c/mi2cv.c b/drivers/mentor/i2c/mi2cv.c
index 1cdcf74..b0270c9 100644
--- a/drivers/mentor/i2c/mi2cv.c
+++ b/drivers/mentor/i2c/mi2cv.c
@@ -81,14 +81,14 @@
 	udelay(1);
 }
 
-static int mentor_i2c_interrupt_get(void)
+static bool mentor_i2c_interrupt_get(void)
 {
 	uint32_t reg;
 
 	/* get the interrupt flag bit */
 	reg = mmio_read_32((uintptr_t)&base->control);
 	reg &= I2C_CONTROL_IFLG;
-	return reg && I2C_CONTROL_IFLG;
+	return (reg != 0U);
 }
 
 static int mentor_i2c_wait_interrupt(void)