OMAP3 SDRC: Fix freeze when scaling CORE dpll to < 83Mhz

This patch fixes a bug in the CORE dpll scaling sequence which was
errouneously clearing some bits in the SDRC DLLA CTRL register and
hence causing a freeze.  The issue was observed only on platforms
which scale CORE dpll to < 83Mhz and hence program the DLL in fixed
delay mode.

Issue reported by Limei Wang <E12499@motorola.com>, with debugging
assistance from Richard Woodruff <r-woodruff2@ti.com> and Girish
Ghongdemath <girishsg@ti.com>.
Signed-off-by: NRajendra Nayak <rnayak@ti.com>
Cc: Limei Wang <E12499@motorola.com>
Cc: Richard Woodruff <r-woodruff2@ti.com>
Cc: Girish Ghongdemath <girishsg@ti.com>
Signed-off-by: NPaul Walmsley <paul@pwsan.com>
[paul@pwsan.com: updated patch description to include collaboration credits]

arch/arm/mach-omap2/sram34xx.S

@@ -143,7 +143,7 @@ return_to_sdram:
 unlock_dll:
 	ldr	r11, omap3_sdrc_dlla_ctrl
 	ldr	r12, [r11]
-	and	r12, r12, #FIXEDDELAY_MASK
+	bic	r12, r12, #FIXEDDELAY_MASK
 	orr	r12, r12, #FIXEDDELAY_DEFAULT
 	orr	r12, r12, #DLLIDLE_MASK
 	str	r12, [r11]		@ (no OCP barrier needed)