x86: unification of cfufreq/Kconfig

Merge the two Kconfig files to a single file.

Checked using make allmodconfig for x86_64.
No changes in build.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Adrian Bunk <bunk@kernel.org>
Cc: Dave Jones <davej@codemonkey.org.uk>