ARM: OMAP4: Fix definition of IS_PM44XX_ERRATUM

Just like IS_PM34XX_ERRATUM, IS_PM44XX_ERRATUM is valid only if
CONFIG_PM is enabled, else, disabling CONFIG_PM results in build
failure complaining about the following:
arch/arm/mach-omap2/built-in.o: In function `omap4_boot_secondary':
:(.text+0x8a70): undefined reference to `pm44xx_errata'

Fixes: c962184 (ARM: OMAP4: PM: add errata support)
Reported-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.ocm>
Acked-by: Kevin Hilman <khilman@linaro.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/mach-omap2/pm.h

@@ -103,7 +103,7 @@ static inline void enable_omap3630_toggle_l2_on_restore(void) { }
 
 #define PM_OMAP4_ROM_SMP_BOOT_ERRATUM_GICD	(1 << 0)
 
-#if defined(CONFIG_ARCH_OMAP4)
+#if defined(CONFIG_PM) && defined(CONFIG_ARCH_OMAP4)
 extern u16 pm44xx_errata;
 #define IS_PM44XX_ERRATUM(id)		(pm44xx_errata & (id))
 #else