RDMA/erdma: Allocate doorbell resources from hardware

RDMA/erdma: Allocate doorbell resources from hardware

Each ucontext will try to allocate doorbell resources in the extended bar
space from hardware. For compatibility, we change nothing for the original
bar space, and it will be used only for applications with CAP_SYS_RAWIO
authority in the older HW/FW environments.

Signed-off-by: Cheng Xu <chengyou@linux.alibaba.com>
Link: https://lore.kernel.org/r/20230606055005.80729-3-chengyou@linux.alibaba.com
Signed-off-by: Leon Romanovsky <leon@kernel.org>