"\s" is not an escape sequence in a Perl double-quoted string, so the
pwm feature emits its select statement without the leading tab that
every other feature gets. Kconfig accepts the unindented line, but the
generated target/Config.in is inconsistent.
Fixes: f6fbc39706 ("build: define PWM_SUPPORT arch feature flag")
Signed-off-by: Daniel Golle <daniel@makrotopia.org>