Input: wistron_btns - disable on UML

Input: wistron_btns - disable on UML

The wistron_btns driver calls rtc_cmos_read(), which isn't
available with UML builds, so disable this driver on UML.

Prevents this build error:

ld: drivers/input/misc/wistron_btns.o: in function `poll_bios':
wistron_btns.c:(.text+0x4be): undefined reference to `rtc_cmos_read'

Fixes: 0bbadafdc49d ("um: allow disabling NO_IOMEM") # v5.14+
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/r/20221130161604.1879-1-rdunlap@infradead.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>