usb: pd: Don't reject sink request based on max current

A fixed sink PDO request includes both operating current and
max current. Although the max current requested may be greater
than the available source advertisement, as per spec only the
operating current request needs to be considered. The sink will
likely have also set the Capability Mismatch bit as well. Hence,
don't reject the request otherwise the sink will keep
re-requesting and never enter a contract.

Change-Id: Ia15e2e17abe43f2bcbc1fe7011b70ab0e0f5d9eb
Signed-off-by: Jack Pham <jackp@codeaurora.org>