BACKPORT: cbfs_core.c: make cfbs searches even less verbose

BACKPORT: cbfs_core.c: make cfbs searches even less verbose

The cbfs core code would print out the name of the file it is
searching for and when it is found would print out the name
again. This contributes to a lot of unnecessary messages in a
functioning payload’s output. Change this message to a DEBUG one
so that it will only be printed when CONFIG_DEBUG_CBFS is enabled.

BUG=None
BRANCH=None
TEST=Compiled and booted.

Change-Id: I142166bfdfcb5e7f6dba6c1ecbd13f3c0ff15088
Signed-off-by: Dave Frodin <dave.frodin@se-eng.com>
Reviewed-on: https://gerrit.chromium.org/gerrit/50459
Reviewed-by: Stefan Reinauer <reinauer@google.com>
Commit-Queue: Aaron Durbin <adurbin@chromium.org>
Tested-by: Aaron Durbin <adurbin@chromium.org>