8139too: [cosmetic] fix incorrect register for flash-rom

I would like to submit a correction to the driver

     drivers/net/8139too.c,

which in no way changes the compiled driver, but does change
the value of a previously incorrect value for the configuration
register address of Flash PROM on the network processor rtl8139C.
This corrected value is in accordance with the datasheet
for rtl8139C, and in addition this new value is indeed used
in other functional drivers that use this adapter for
programming a Flash memory chip in situ. But as said,
the two new constants are never referenced in the driver
maintained by you: they are only informational and correct!

Mats Erik Andersson, meand@users.sourceforge.net

Signed-off-by: Jeff Garzik <jgarzik@redhat.com>