drivers/net/e1000e: fix sparse warnings: make symbols static

Fix this sparse warnings:

  drivers/net/e1000e/es2lan.c:1265:5: warning: symbol 'e1000_read_kmrn_reg_80003es2lan' was not declared. Should it be static?
  drivers/net/e1000e/es2lan.c:1298:5: warning: symbol 'e1000_write_kmrn_reg_80003es2lan' was not declared. Should it be static?

Signed-off-by: Hannes Eder <hannes@hanneseder.net>
Signed-off-by: David S. Miller <davem@davemloft.net>