usb: musb: remove generic_interrupt

This patch is based on the discussion of a previous patch to fix an issue
where the omap2430 musb driver is not working for N9/N950.

Moving all the interrupt handling to the devices. Avoids inclusion of generic
interrupt and breakage due to sometimes misleading CONFIG options. This makes
sure usb always works if on of the subdrivers is chosen. Tested on Nokia N9/N950.

Partially clean up CONFIG_SOC_OMAP3430 which is not necessary in the cases
where I removed it. Also helps with the removal work of those options that
Tony Lindgren predicted would happen at some point.

Signed-off-by: Philippe De Swert <philippe.deswert@jollamobile.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>