ARMV7: Fix udelay for OMAP4

The OMAP4 x-load code sets gptimer1 clock source to 32Khz.  This isn't
acceptable for udelay.  This patch changes from gptimer1 to gptimer2,
which uses sys_clk at 38.4 Mhz.

Signed-off-by: Steve Sakoman <steve@sakoman.com>
Signed-off-by: Sandeep Paulraj <s-paulraj@ti.com>