ARM: at91: common: guard ATMEL_PIT code by ifdef

Atmel PIT timer is not available for next products that
have another timer hardware block.
To be able to use the common at91 code, guard the code that uses PIT
by ifdefs.

Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
diff --git a/arch/arm/mach-at91/armv7/cpu.c b/arch/arm/mach-at91/armv7/cpu.c
index a8f4356..8b73550 100644
--- a/arch/arm/mach-at91/armv7/cpu.c
+++ b/arch/arm/mach-at91/armv7/cpu.c
@@ -29,6 +29,7 @@
 
 void arch_preboot_os(void)
 {
+#if (IS_ENABLED(CONFIG_ATMEL_PIT_TIMER))
 	ulong cpiv;
 	at91_pit_t *pit = (at91_pit_t *)ATMEL_BASE_PIT;
 
@@ -40,6 +41,7 @@
 	 * without waiting for wrapping back to 0
 	 */
 	writel(cpiv + 0x1000, &pit->mr);
+#endif
 }
 
 #if defined(CONFIG_DISPLAY_CPUINFO)