RDMA/bnxt_re: Enable atomics only if host bios supports

Driver shall check if the host system bios has enabled
Atomic operations capability in PCI Device Control 2
register of the pci-device. Expose the ATOMIC_HCA
flag only if the Atomic operations capability is set.

Signed-off-by: Devesh Sharma <devesh.sharma@broadcom.com>
Signed-off-by: Selvin Xavier <selvin.xavier@broadcom.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>