bnxt_en: Reduce memory usage when running in kdump kernel.

Skip RDMA context memory allocations, reduce to 1 ring, and disable
TPA when running in the kdump kernel.  Without this patch, the driver
fails to initialize with memory allocation errors when running in a
typical kdump kernel.

Fixes: cf6daed0

 ("bnxt_en: Increase context memory allocations on 57500 chips for RDMA.")
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>