USB: gadget: pxa27x_udc.c: cleanup kernel-doc

no argument named @index in pio_irq_disable, and
no argument named @req in inc_ep_stats_bytes,
remove them.

Signed-off-by: Qinghuang Feng <qhfeng.kernel@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>