USB: mos7840: Fix compilation of usb serial driver

The __devinitconst section can't be referenced
from usb_serial_device structure. Thus removed it as
it done in other mos* device drivers.

Error itself:
WARNING: drivers/usb/serial/mos7840.o(.data+0x8): Section mismatch in reference
from the variable moschip7840_4port_device to the variable
.devinit.rodata:id_table
The variable moschip7840_4port_device references
the variable __devinitconst id_table

[v2] no attach now

Signed-off-by: Tony Zelenoff <antonz@parallels.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>