um: Fix build w/o CONFIG_PM_SLEEP

stable inclusion
from stable-v5.10.185
commit ed2bf5cee6c6d5dc788ef19e8b984182c594d3ec
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8L5XP

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ed2bf5cee6c6d5dc788ef19e8b984182c594d3ec



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commit 1fb1abc8 upstream.

uml_pm_wake() is unconditionally called from the SIGUSR1 wakeup
handler since that's in the userspace portion of UML, and thus
a bit tricky to ifdef out. Since pm_system_wakeup() can always
be called (but may be an empty inline), also simply always have
uml_pm_wake() to fix the build.

Reported-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: sanglipeng <sanglipeng1@jd.com>