usb: remove COMPAT_32BIT ifdefs

Now that we have proper 32-bit compat support, remove COMPAT_32BIT
ifdefs to allow 32-bit code to use the 64-bit layout of USB ioctl
structs and struct usb_fs_endpoint.

This includes the removal of redundant alignment directives that had
no effect in practice.

Reviewed by: hselasky, jrtc27 (prior version)