USB: musb: davinci dm6446evm GPIO renumbering

Numbering for GPIOs on the pcf857x chips on the dm644x EVM board
changed when DaVinci chips with more GPIOs were supported.  Update
the GPIO number used for nVBUS_DRV.

Longer term, we need a better abstraction of board-specific setup in
this code so we're not hard-coding board specific GPIOs into the
driver, but for now this at least gets it back to working with
mainline davinci core code.

Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>