camera2: Make debug log for ReprocessFormatsMap more readable

Since the image format is in hex, add 0x.

Bug: N/A

Test: build

Flag: EXEMPT; log format fix

Change-Id: I8340d9264212fd593ff52d7bcc6df3ba43d34d81
Signed-off-by: Jayant Chowdhary <jchowdhary@google.com>