RDS/IB: Fix crash in SRQ initialization

RDS/IB: Fix crash in SRQ initialization

SRQ initialization causes crash when IC connection is not available.

Orabug: 23523586

This is regression fix for commit 0f0f08915.
We require more work to have SRQ working with variable fragment size.
For now, we fix crash in SRQ initialization.

This also adds warning when SRQ is enabled.
SRQ feature is experimental and disabled by default.
When any user enables it, we should give warning.

Signed-off-by: Ajaykumar Hotchandani <ajaykumar.hotchandani@oracle.com>
Tested-by: jenny x.xu <jenny.x.xu@oracle.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>