bnxt_en: Combine 2 functions calling the same HWRM_DRV_RGTR fw command.

Everytime driver registers with firmware, driver is required to
register for async event notifications as well. These 2 calls
are done using the same firmware command and can be combined.

We are also missing the 2nd step to register for async events
in the suspend/resume path and this will fix it.  Prior to this,
we were getting only default notifications.

ULP can register for additional async events for the RDMA driver,
so we add a parameter to the new function to only do step 2 when
it is called from ULP.

Signed-off-by: Vasundhara Volam <vasundhara-v.volam@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>