usb: Add export.h for EXPORT_SYMBOL/THIS_MODULE where needed

With module.h being implicitly everywhere via device.h, the absence
of explicitly including something for EXPORT_SYMBOL went unnoticed.
Since we are heading to fix things up and clean module.h from the
device.h file, we need to explicitly include these files now.

Use the lightweight version of the header that has just THIS_MODULE
and EXPORT_SYMBOL variants.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>