ena: Update ena_com_update_intr_reg API usage

This commit fixes the usage of this function to be compatible with the
new API introduced by ena-com update to v2.7.0

Approved by: cperciva (mentor)
MFC after: 2 weeks
Sponsored by: Amazon, Inc.

(cherry picked from commit 72e34ebdd08854dc896f267b0461e241c4040241)