dm: core: Fix incorrect flag check

The test should be checking whether $flags are non-zero and $drv_flags
contain specific flags, however these two sets of flags are separate,
and the two tests should be logically ANDed, not bitwise ANDed.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Simon Glass <sjg@chromium.org>
Reviewed-by: Simon Glass <sjg@chromium.org>