ethtool: cmis_cdb: use correct rpl size in ethtool_cmis_module_poll()

In the Linux kernel, the following vulnerability has been resolved:

ethtool: cmis_cdb: use correct rpl size in ethtool_cmis_module_poll()

rpl is passed as a pointer to ethtool_cmis_module_poll(), so the correct
size of rpl is sizeof(*rpl) which should be just 1 byte. Using the
pointer size instead can cause stack corruption:

Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: ethtool_cmis_wait_for_cond+0xf4/0x100
CPU: 72 UID: 0 PID: 4440 Comm: kworker/72:2 Kdump: loaded Tainted: G OE 6.11.0 #24
Tainted: [O]=OOT_MODULE, [E]=UNSIGNED_MODULE
Hardware name: Dell Inc. PowerEdge R760/04GWWM, BIOS 1.6.6 09/20/2023
Workqueue: events module_flash_fw_work
Call Trace:
<TASK>
panic+0x339/0x360
? ethtool_cmis_wait_for_cond+0xf4/0x100
? __pfx_status_success+0x10/0x10
? __pfx_status_fail+0x10/0x10
__stack_chk_fail+0x10/0x10
ethtool_cmis_wait_for_cond+0xf4/0x100
ethtool_cmis_cdb_execute_cmd+0x1fc/0x330
? __pfx_status_fail+0x10/0x10
cmis_cdb_module_features_get+0x6d/0xd0
ethtool_cmis_cdb_init+0x8a/0xd0
ethtool_cmis_fw_update+0x46/0x1d0
module_flash_fw_work+0x17/0xa0
process_one_work+0x179/0x390
worker_thread+0x239/0x340
? __pfx_worker_thread+0x10/0x10
kthread+0xcc/0x100
? __pfx_kthread+0x10/0x10
ret_from_fork+0x2d/0x50
? __pfx_kthread+0x10/0x10
ret_from_fork_asm+0x1a/0x30
</TASK>