USB: gadget: storage: reuse definitions from scsi.h header file

This commit changes storage_common.h, file_storage.c and
f_mass_storage.c to use definitions of SCSI commands from
scsi/scsi.h file instead of redefining the commands in
storage_common.c.

scsi/scsi.h header file was missing READ_FORMAT_CAPACITIES and
READ_HEADER so this commit also add those to the header.

Signed-off-by: Michal Nazarewicz <mina86@mina86.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: James Bottomley <James.Bottomley@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>