perf/x86/Kconfig: Fix indentation in the Kconfig file

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.
Signed-off-by: Juerg Haefliger <juerg.haefliger@canonical.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20220525133949.53730-1-juerg.haefliger@canonical.com