m4: display: enable clocks when sending panel commands

Gets rid of these:
<3>[    5.684663] mipi_dsi_cmd_dma_tx: dma timeout error

Adapted from m7 panel driver.
m4: display: remove duplicate MIPI device registration

Fixes these two warnings:
------------[ cut here ]------------
WARNING: at ../../../../../../kernel/htc/msm8960/fs/sysfs/dir.c:508
sysfs_add_one+0x94/0xb4()
sysfs: cannot create duplicate filename '/devices/platform/mipi_m4.0'
<snip>
---[ end trace 1e53ee17c79f546d ]---
------------[ cut here ]------------
WARNING: at ../../../../../../kernel/htc/msm8960/lib/kobject.c:198
kobject_add_internal+0x17c/0x228()
kobject_add_internal failed for mipi_m4.0 with -EEXIST, don't try to
register things with the same name in the same directory.
<snip>
---[ end trace 1e53ee17c79f546e ]---