msm: vidc: Fix Hier-p settings in driver

When HEVC Hier-P is enabled with 6 layers v4l2 framework reject the
setting as max value is only 3 layers. Also when LTR is configured
Hier-P is toggled this will result in resetting Hier-P layers if set,
this will erase earlier configured Hier-P settings. This change fixes
the Hier-P issues seen in driver.

Change-Id: Ie0206c725323e8fcb82937fb5885ca0c67a49b1f
Signed-off-by: Ashray Kulkarni <ashrayk@codeaurora.org>