disp: msm: sde: enable reg write only for debug defconfig

Write to hardware registers should be exposed for only debug
purpose. Hence use CONFIG_DYNAMIC_DEBUG to restrict register
writes only for debug defconfig.

Change-Id: I0b67b46a69920f6620570ace9d4faf732076126d
Signed-off-by: Lakshmi Narayana Kalavala <lkalaval@codeaurora.org>