RDMA/bnxt_re: Refactor stats context memory allocation

RDMA/bnxt_re: Refactor stats context memory allocation

Moved the stats context allocation logic to a new function.
The stats context memory allocation code has been moved from
bnxt_qplib_alloc_hwctx() to the newly added bnxt_re_get_stats_ctx()
function. Also, the code to send the firmware command has been moved.

This patch is in preparation for other patches in this series.
There is no functional changes intended.

Signed-off-by: Kalesh AP <kalesh-anakkur.purayil@broadcom.com>
Link: https://patch.msgid.link/20250822040801.776196-5-kalesh-anakkur.purayil@broadcom.com
Signed-off-by: Leon Romanovsky <leon@kernel.org>