OMAP2/3/4 clock: omap2_clk_prepare_for_reboot() is OMAP2xxx-only

omap2_clk_prepare_for_reboot() is only applicable to OMAP2xxx chips,
so rename it to omap2xxx_clk_prepare_for_reboot() and only call it when
running on OMAP2xxx chips.  Remove the old stub in the OMAP3 clock code.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
diff --git a/arch/arm/mach-omap2/clock2xxx.c b/arch/arm/mach-omap2/clock2xxx.c
index e98f48b..a48b01a 100644
--- a/arch/arm/mach-omap2/clock2xxx.c
+++ b/arch/arm/mach-omap2/clock2xxx.c
@@ -71,7 +71,7 @@
 /*
  * Set clocks for bypass mode for reboot to work.
  */
-void omap2_clk_prepare_for_reboot(void)
+void omap2xxx_clk_prepare_for_reboot(void)
 {
 	u32 rate;