soc: aspeed: uart-routing: Use __sysfs_match_string

soc: aspeed: uart-routing: Use __sysfs_match_string

The existing use of match_string() caused it to reject 'echo foo' due
to the implicitly appended newline, which was somewhat ergonomically
awkward and inconsistent with typical sysfs behavior.  Using the
__sysfs_* variant instead provides more convenient and consistent
linefeed-agnostic behavior.

Signed-off-by: Zev Weiss <zev@bewilderbeest.net>
Fixes: c6807970c3bc ("soc: aspeed: Add UART routing support")
Reviewed-by: Joel Stanley <joel@jms.id.au>
Link: https://lore.kernel.org/r/20230628083735.19946-2-zev@bewilderbeest.net
Signed-off-by: Joel Stanley <joel@jms.id.au>
Link: https://lore.kernel.org/r/20230810122941.231085-1-joel@jms.id.au
Signed-off-by: Arnd Bergmann <arnd@arndb.de>