soc/marvell/mvmap2315: Fix integer arithmetic

Replace logical with bitwise AND operator.

Change-Id: I712fab61fbbc833fc2b2575948a875e2f07fd5de
Reported-by: Coverity (CID 1362808)
Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Reviewed-on: https://review.coreboot.org/17401
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

src/soc/marvell/mvmap2315/mcu.c

@@ -31,7 +31,7 @@ static u8 mvmap2315_calc_checksum(const void  *data, u32 size)
 	for (i = csum = 0; i < size; i++)
 		csum += bytes[i];
 
-	return (~csum) && 0xFF;
+	return (~csum) & 0xFF;
 }
 
 void mcu_irq(void)