Revert "ARM: pxa: add dummy clock for sa1100-rtc"

This reverts commit 7557c175f6.

This revert is necessary to revert the broken "RTC: sa1100:
support sa1100, pxa and mmp soc families" change.

arch/arm/mach-pxa/pxa300.c

@@ -89,7 +89,6 @@ static DEFINE_PXA3_CKEN(gcu, PXA300_GCU, 0, 0);
 static struct clk_lookup common_clkregs[] = {
 	INIT_CLKREG(&clk_common_nand, "pxa3xx-nand", NULL),
 	INIT_CLKREG(&clk_gcu, "pxa3xx-gcu", NULL),
-	INIT_CLKREG(&clk_dummy, "sa1100-rtc", NULL),
 };
 
 static DEFINE_PXA3_CKEN(pxa310_mmc3, MMC3, 19500000, 0);