clocksource: convert OMAP1 to 32-bit down counting clocksource

Convert the OMAP1 32-bit down counting clocksource to the generic
clocksource infrastructure.

Tested-by: Tony Lindgren <tony@atomide.com>
Cc: linux-omap@vger.kernel.org
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/plat-omap/Kconfig b/arch/arm/plat-omap/Kconfig
index cd5f993..e9c0efc 100644
--- a/arch/arm/plat-omap/Kconfig
+++ b/arch/arm/plat-omap/Kconfig
@@ -12,6 +12,7 @@
 config ARCH_OMAP1
 	bool "TI OMAP1"
 	select CLKDEV_LOOKUP
+	select CLKSRC_MMIO
 	help
 	  "Systems based on omap7xx, omap15xx or omap16xx"