OMAP: UART: don't resume UARTs that are not enabled.

Add additional check to omap_uart_resume_idle() so that only
enabled (specifically, idle-enabled) UARTs are allowed to resume.
This matches the existing check in prepare idle.

Without this patch, the system will hang if a board is
configured to register only some uarts instead of all of
them and PM is enabled.

Cc: Govindraj R. <[e-mail]>
Signed-off-by: Kevin Hilman <[e-mail]>
[[e-mail]: updated description]
Signed-off-by: Tony Lindgren <[e-mail]>

arch/arm/mach-omap2/serial.c

···
 	struct omap_uart_state *uart;
 
 	list_for_each_entry(uart, &uart_list, node) {
-		if (num == uart->num) {
+		if (num == uart->num && uart->can_sleep) {
 			omap_uart_enable_clocks(uart);
 
 			/* Check for IO pad wakeup */