net: dsa: qca8k: fix noderef.cocci warnings

drivers/net/dsa/qca8k.c:422:37-43: ERROR: application of sizeof to pointer

 sizeof when applied to a pointer typed expression gives the size of
 the pointer

Generated by: scripts/coccinelle/misc/noderef.cocci

Fixes: 90386223 ("net: dsa: qca8k: add support for larger read/write size with mgmt Ethernet")
CC: Ansuel Smith <ansuelsmth@gmail.com>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: kernel test robot <lkp@intel.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20220209221304.GA17529@d2214a582157


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