drm/msm/phy/dsi_phy: silence -EPROBE_DEFER warnings

The following errors show up when booting the Nexus 5:

msm_dsi_phy fd922a00.dsi-phy: [drm:dsi_phy_driver_probe] *ERROR*
 dsi_phy_regulator_init: failed to init regulator, ret=-517
msm_dsi_phy fd922a00.dsi-phy: [drm:dsi_phy_driver_probe] *ERROR*
 dsi_phy_driver_probe: failed to init regulator

dsi_phy_regulator_init() already logs the error, so no need to log
the same error a second time in dsi_phy_driver_probe(). This patch
also changes dsi_phy_regulator_init() to not log the error if the
error code is -EPROBE_DEFER to reduce noise in dmesg.

Signed-off-by: Brian Masney <masneyb@onstation.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
[add some {}'s]
Signed-off-by: Rob Clark <robdclark@chromium.org>