n9: added LP5521 LED driver

For (currently) unknown reason N9 "Indicator LED" stays on after the
boot process. According to schematics LED can be turned on by either
LP5521 or TWL5031 (but only if there is something powering USB port)
Both of these chips seem to work OK, but LED is still turned on.
USB options related to OTG functionality enabled in 2.6 were also
added.

Signed-off-by: Filip Matijević <filip.matijevic.pz@gmail.com>
n9: add support for volume up/down keys

Signed-off-by: Filip Matijević <filip.matijevic.pz@gmail.com>
n9: fix for reboot when something is plugged into 3.5mm jack

N9 would reboot due to irq storm (sched: RT throttling activated)
when something is plugged into 3.5mm jack.
Couple of kernel warnings (gpio_get_value and pm_qos_remove_request)
were also fixed.

Signed-off-by: Filip Matijević <filip.matijevic.pz@gmail.com>