usb: usbtmc: Add ioctl for EOM bit

add USBTMC_IOCTL_EOM_ENABLE to specify EOM bit for next write()
call. Sets Bit 0 of field 'bmTransferAttributes' of DEV_DEP_MSG_OUT
Bulk-OUT Header.
Allows fine grained control over end of message handling on a
per file descriptor basis.

Reviewed-by: Steve Bayless <steve_bayless@keysight.com>
Tested-by: Dave Penkler <dpenkler@gmail.com>
Signed-off-by: Dave Penkler <dpenkler@gmail.com>
Signed-off-by: Guido Kiener <guido.kiener@rohde-schwarz.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>