ARM: omap: fix uninformative vc/i2c configuration error message

On my OMAP4 platform, I'm getting this error message repeated several
times at boot:

omap_vc_i2c_init: I2C config for all channels must match.
omap_vc_i2c_init: I2C config for all channels must match.

This doesn't help identify what the problem is.  Fix this message to
be more informative:

omap_vc_i2c_init: I2C config for vdd_iva does not match other channels (0).
omap_vc_i2c_init: I2C config for vdd_mpu does not match other channels (0).

This allows us to identify which voltage domains have a problem, and
what the I2C configuration state (a boolean, i2c_high_speed) setting
being used actually is.

From this we find that omap4_core_pmic has i2c_high_speed false, but
omap4_iva_pmic and omap4_mpu_pmic both have it set true.

Acked-by: Tony Lindgren <tony@atomide.com>
Acked-by: Kevin Hilman <khilman@ti.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/mach-omap2/vc.c

@@ -265,8 +265,8 @@ static void __init omap_vc_i2c_init(struct voltagedomain *voltdm)
 
 	if (initialized) {
 		if (voltdm->pmic->i2c_high_speed != i2c_high_speed)
-			pr_warn("%s: I2C config for all channels must match.",
-				__func__);
+			pr_warn("%s: I2C config for vdd_%s does not match other channels (%u).",
+				__func__, voltdm->name, i2c_high_speed);
 		return;
 	}