eth: fbnic: Replace kzalloc/fbnic_fw_init_cmpl with fbnic_fw_alloc_cmpl

Replace the pattern of calling and validating kzalloc then
fbnic_fw_init_cmpl with a single function, fbnic_fw_alloc_cmpl.

Signed-off-by: Lee Trager <lee@trager.us>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://patch.msgid.link/20250516164804.741348-1-lee@trager.us


Signed-off-by: Jakub Kicinski <kuba@kernel.org>