arch/x86/um: remove depends on CONFIG_EXPERIMENTAL

arch/x86/um: remove depends on CONFIG_EXPERIMENTAL

The CONFIG_EXPERIMENTAL config item has not carried much meaning for a
while now and is almost always enabled by default. As agreed during the
Linux kernel summit, remove it from any "depends on" lines in Kconfigs.

CC: Jeff Dike <jdike@addtoit.com>
CC: Richard Weinberger <richard@nod.at>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Ingo Molnar <mingo@redhat.com>
CC: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Richard Weinberger <richard@nod.at>