net: ethernet: mtk_eth_soc: remove unused variable 'count'

GCC reports the following warning with W=1:

drivers/net/ethernet/mediatek/mtk_ppe_debugfs.c:80:9: warning:
 variable 'count' set but not used [-Wunused-but-set-variable]
   80 |  int i, count;
      |         ^~~~~

This variable is not used in function , this commit
remove it to fix the warning.

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Qiheng Lin <linqiheng@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>