omap: Fix gpio_resume_after_retention

For omap4 case, this was wrongly writing GPIO_LEVELDETECTx
registers with OMAP24XX_ offset and OMAP4_ offset.

Bug introduced in commit:

  commit 3f1686a9bfe74979c6ad538c78039730f665f77e
  Author: Tony Lindgren <tony@atomide.com>
  Date:   Mon Feb 15 09:27:25 2010 -0800

      omap: Fix gpio.c for multi-omap for omap4

Signed-off-by: Sergio Aguirre <saaguirre@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>