ARM: OMAP2+: PRM: initialize en_uart4_mask and grpsel_uart4_mask

In the case where has_uart4 is false, en_uart4_mask and grpsel_uart4_mask
are not initialized and so any garbage value is being logically or'd into
the write of PM_WKEN and OMAP3430_PM_MPUGRPSEL.  Fix this by initializing
these masks to zero.
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/mach-omap2/prm3xxx.c

@@ -319,6 +319,9 @@ void __init omap3_prm_init_pm(bool has_uart4, bool has_iva)
 	if (has_uart4) {
 		en_uart4_mask = OMAP3630_EN_UART4_MASK;
 		grpsel_uart4_mask = OMAP3630_GRPSEL_UART4_MASK;
+	} else {
+		en_uart4_mask = 0;
+		grpsel_uart4_mask = 0;
 	}
 
 	/* Enable wakeups in PER */