usb: musb: core: kill unneeded #include's

musb_core.c #include's a bunch of ARM and DaVinci specific headers, goodness
knows why -- it happily compiles without them...

Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>