pinctrl: add the DM_UC_FLAG_SEQ_ALIAS flag for numbering the devices

It is possible to have multiple pin controllers in the system. Use the
DM_UC_FLAG_SEQ_ALIAS flag so that the pinctrl instances are assigned
a sequence number.

Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Simon Glass <sjg@chromium.org>
Signed-off-by: Thomas Abraham <thomas.ab@samsung.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>