drivers: net: aquantia: fix unsigned compared against 0

Change the reg variable to not be unsigned so that we not get into an
unsigned compared against 0.

Signed-off-by: Cosmin-Florin Aluchenesei <aluchenesei.cosmin-florin@nxp.com>
Reviewed-by: Ramon Fried <rfried.dev@gmail.com>
1 file changed