Fetch credits received.Applicable if fetch credits are enabled in the software context.
The credit descriptor context is for internal DMA use only and can be read
from the indirect bus for debug. This context stores credits for each queue that
have been received through the Descriptor Credit Interface with the CREDIT_ADD
operation. If the credit operation has the
dsc_crdt_in_fence bit set to 1, credits are added only as the read
request for the descriptor is generated.