camera: isp: do reg update only once at initial configure

Remove reg update in the end of preparing the first configuration
packet since reg update will be done again when camif and rdi resources
starts.

CRs-fixed: 2090188
Change-Id: Ibc9054e017debc3000c81f5ed74a6c6ad79391fe
Signed-off-by: Junzhe Zou <jnzhezou@codeaurora.org>