serial: pch_uart: Fix build warning when CONFIG_DEBUG_FS=n

Add CONFIG_DEBUG_FS to 'char name' in order to fix the following
build warning, because 'char name' is used only when CONFIG_DEBUG_FS
is enabled.

drivers/tty/serial/pch_uart.c:1765:7: warning: unused variable 'name' [-Wunused-variable]

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>