octeontx2-af: Increase link credit restore polling timeout

It's been observed that sometimes link credit restore takes
a lot of time than the current timeout. This patch increases
the default timeout value and return the proper error value
on failure.

Fixes: 1c74b891

 ("octeontx2-af: Wait for TX link idle for credits change")
Signed-off-by: Geetha sowjanya <gakula@marvell.com>
Signed-off-by: Subbaraya Sundeep <sbhatta@marvell.com>
Signed-off-by: Sunil Goutham <sgoutham@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>