coding style: use ARRAY_SIZE() when possible

We have the macro ARRAY_SIZE() already available. Use it!

Issue identified by checkpatch script from Linux kernel v5.1 using
the command

	find src/ -type f -exec ./tools/scripts/checkpatch.pl \
	-q --types ARRAY_SIZE -f {} \;

Change-Id: Ic7da9b710edf118eacb08f9e222f34208c580842
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: http://openocd.zylin.com/5198
Tested-by: jenkins
Reviewed-by: Tomas Vanek <vanekt@fbl.cz>

src/flash/nor/psoc6.c

@@ -108,7 +108,7 @@ static const struct row_region safe_sflash_regions[] = {
 	{0x16007C00, 0x400},	/* SFLASH: TOC2 */
 };
 
-#define SFLASH_NUM_REGIONS (sizeof(safe_sflash_regions) / sizeof(safe_sflash_regions[0]))
+#define SFLASH_NUM_REGIONS ARRAY_SIZE(safe_sflash_regions)
 
 static struct working_area *g_stack_area;
 static struct armv7m_algorithm g_armv7m_info;