serial: sifive: Remove redundant of_match_ptr()

The driver depends on CONFIG_OF, it is not necessary to use
of_match_ptr() here.

Signed-off-by: Ruan Jinjie <ruanjinjie@huawei.com>
Link: https://lore.kernel.org/r/20230809085541.2969654-1-ruanjinjie@huawei.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>