msm: camera: memmgr: update correct length in bufq

In a corner case race condition to free the original
ion buf allocated and new ion buffer with same fd but
different size after freeing the origianl ion buf might
result into mismatches in the real ion buf size assigned
in bufq. To avoid this update length in bufq with
local variable.

Bug: 235113793
Test: build pass, local verify camera function
CRs-Fixed: 3142221
Change-Id: I0c76f7124de0cf5389592595872e695e07fc24d7
Signed-off-by: Tejas Prajapati <quic_tpraja@quicinc.com>
Signed-off-by: Nick Chung <nickchung@google.com>