tile: fix build failure

When building with allmodconfig the build was failing with the error:

arch/tile/kernel/usb.c:70:1: warning: data definition has no type or storage class [enabled by default]
arch/tile/kernel/usb.c:70:1: error: type defaults to 'int' in declaration of 'arch_initcall' [-Werror=implicit-int]
arch/tile/kernel/usb.c:70:1: warning: parameter names (without types) in function declaration [enabled by default]
arch/tile/kernel/usb.c:63:19: warning: 'tilegx_usb_init' defined but not used [-Wunused-function]

Include linux/module.h to resolve the build failure.

Signed-off-by: Sudip Mukherjee <sudip@vectorindia.org>
Signed-off-by: Chris Metcalf <cmetcalf@ezchip.com>