ARM: OMAP2+: Fix omap off idle power consumption creeping up

If we use a combination of VMODE and I2C4 for retention modes,
eventually the off idle power consumption will creep up by about
23mW, even during off mode with I2C4 always staying enabled.

Turns out this is because of erratum i531 "Extra Power Consumed
When Repeated Start Operation Mode Is Enabled on I2C Interface
Dedicated for Smart Reflex (I2C4)" as pointed out by Nishanth
Menon <nm@ti.com>.

Let's fix the issue by adding i2c_cfg_clear_mask for the bits
to clear when initializing the I2C4 adapter so we can clear
SREN bit that drives the I2C4 lines low otherwise when there
is no traffic.

Fixes: 3b8c4ebb7630 ("ARM: OMAP3: Fix idle mode signaling for
Cc: stable@vger.kernel.org # v3.16+
sys_clkreq and sys_off_mode")
Cc: Kevin Hilman <khilman@kernel.org>
Cc: Tero Kristo <t-kristo@ti.com>
Reviewed-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
diff --git a/arch/arm/mach-omap2/prm-regbits-34xx.h b/arch/arm/mach-omap2/prm-regbits-34xx.h
index cbefbd7..661d753 100644
--- a/arch/arm/mach-omap2/prm-regbits-34xx.h
+++ b/arch/arm/mach-omap2/prm-regbits-34xx.h
@@ -112,6 +112,7 @@
 #define OMAP3430_VC_CMD_ONLP_SHIFT			16
 #define OMAP3430_VC_CMD_RET_SHIFT			8
 #define OMAP3430_VC_CMD_OFF_SHIFT			0
+#define OMAP3430_SREN_MASK				(1 << 4)
 #define OMAP3430_HSEN_MASK				(1 << 3)
 #define OMAP3430_MCODE_MASK				(0x7 << 0)
 #define OMAP3430_VALID_MASK				(1 << 24)