greybus: drop a bogus semicolon

Coccinelle reports that gb_svc_pwrmon_debugfs_init() has a block of
a for loop which is followed by an unnecessary semicolon.  Get rid
of that semicolon.

Signed-off-by: Alex Elder <elder@linaro.org>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>