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 <[e-mail]>
Signed-off-by: Tony Lindgren <[e-mail]>

arch/arm/mach-omap2/prm3xxx.c

···
 	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 */