net: phy: Fix overlong PHY timeout

Commit 27c3f70f ("net: phy: Increase link up delay in
genphy_update_link()") increased the per-iteration waiting time from
1ms to 50ms, without adjusting the timeout counter. This lead to the
timeout increasing from the typical 4 seconds to over three minutes.

Adjust the timeout counter evaluation by that factor of 50 to bring the
timeout back to the intended value.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Fixes: net: phy: Increase link up delay in genphy_update_link() ("27c3f70f")
Reviewed-by: Stefan Roese <sr@denx.de>
Tested-by: Matthias Brugger <mbrugger@suse.com>
Tested-by: Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>