ARM: SPEAr: conditionalize l2x0 support

If the cache controller implementation is disabled at build time,
we must not call any functions related to it.

arch/arm/mach-spear/built-in.o: In function `spear13xx_l2x0_init':
arch/arm/mach-spear/spear13xx.c:47: undefined reference to `l2x0_init'
Signed-off-by: NArnd Bergmann <arnd@arndb.de>
Acked-by: NViresh Kumar <viresh.linux@gmail.com>

arch/arm/mach-spear13xx/spear13xx.c

@@ -92,6 +92,8 @@ void __init spear13xx_l2x0_init(void)
 	 * write alloc and 'Full line of zero' options
 	 *
 	 */
+	if (!IS_ENABLED(CONFIG_CACHE_L2X0))
+		return;
 
 	writel_relaxed(0x06, VA_L2CC_BASE + L2X0_PREFETCH_CTRL);