[PATCH for 4.9 42/59] USB: serial: mos7840: fix control-message error handling

From: Johan Hovold [ Upstream commit cd8db057e93ddaacbec025b567490555d2bca280 ] Make sure to detect short transfers when reading a device register. The modem-status handling had sufficient error checks in place, but move handling of short transfers into the register accessor

[PATCH for 4.9 42/59] USB: serial: mos7840: fix control-message error handling

From: Johan Hovold [ Upstream commit cd8db057e93ddaacbec025b567490555d2bca280 ] Make sure to detect short transfers when reading a device register. The modem-status handling had sufficient error checks in place, but move handling of short transfers into the register accessor function itself