net: aquantia: Fill descriptor size and count for channels

Fill descriptor size and count fields of ipa_eth_channel for use by
AQC IPA offload driver.

CRs-Fixed: 2304918
Change-Id: I9ab18419ec0da2469a29354dd2f1aee5a82295af
Signed-off-by: Jinesh K. Jayakumar <jineshk@codeaurora.org>