RDMA/erdma: Refactor the original doorbell allocation mechanism

RDMA/erdma: Refactor the original doorbell allocation mechanism

The original doorbell allocation mechanism is complex and does not meet
the isolation requirement. So we introduce a new doorbell mechanism and the
original mechanism (only be used with CAP_SYS_RAWIO if hardware does not
support the new mechanism) needs to be kept as simple as possible for
compatibility.

Signed-off-by: Cheng Xu <chengyou@linux.alibaba.com>
Link: https://lore.kernel.org/r/20230606055005.80729-5-chengyou@linux.alibaba.com
Signed-off-by: Leon Romanovsky <leon@kernel.org>