msm: kgsl: send ringbuffer NOP padding with the next command

If there isn't enough room at the bottom of the ringbuffer for a
whole command, the remaining space is filled with NOPs and
the command starts again at the top of the ringbuffer, the write
pointer of the ringbuffer shall update accordingly; the existing
implementation sends out in-complete NOP command which may potentially
cause GPU hang. This fix submits the NOP command along with the next
command instead of submitting them separately to have GPU read both
commands in the same fetch.

Change-Id: Ia3c9933c11d986c6743d8026b809bbcb1eaf54bf
Signed-off-by: Zhong Liu <zhongl@codeaurora.org>