octeontx2-af: Fix SDP MAC link credits configuration

Current driver allows only packet size < 512B as SDP_LINK_CREDIT
register is set to default value.
This patch fixes this issue by configure the register with
maximum HW supported value to allow packet size > 512B.

Fixes: 2f7f33a0 ("octeontx2-pf: Add representors for sdp MAC")
Signed-off-by: Geetha sowjanya <gakula@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>