target/arvm7a: Use 'bool' data type where appropriate

The variables are already used as boolean value but have the wrong
data type.

Change-Id: I0f169cac83f6c4094e8d1acb2cb8f1017a96a5d8
Signed-off-by: Marc Schink <dev@zapb.de>
Reviewed-on: https://review.openocd.org/c/openocd/+/9008
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>
Tested-by: jenkins

src/target/armv7a_mmu.c

@@ -214,7 +214,7 @@ COMMAND_HANDLER(armv7a_mmu_dump_table)
 			max_pt_idx -= 1;
 		}
 	} else {
-		if (mmu->cached != 1) {
+		if (!mmu->cached) {
 			LOG_ERROR("TTB not cached!");
 			return ERROR_FAIL;
 		}