x86/Kconfig: Fix indentation and add endif comments to arch/x86/Kconfig

The convention for indentation seems to be a single tab. Help text is
further indented by an additional two whitespaces. Fix the lines that
violate these rules.

While add it, add missing trailing endif comments and squeeze multiple
empty lines.

Signed-off-by: Juerg Haefliger <juerg.haefliger@canonical.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20220525133203.52463-2-juerg.haefliger@canonical.com