bna: remove obsolete use of EXTRA_CFLAGS

EXTRA_CFLAGS should be used on the command line only.

Since EXTRA_CFLAGS here add only a non-existant path to compiler
include paths (by -I), remove EXTRA_CFLAGS completely.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/brocade/bna/Makefile

@@ -9,5 +9,3 @@ obj-$(CONFIG_BNA) += bna.o
 bna-objs := bnad.o bnad_ethtool.o bnad_debugfs.o bna_enet.o bna_tx_rx.o
 bna-objs += bfa_msgq.o bfa_ioc.o bfa_ioc_ct.o bfa_cee.o
 bna-objs += cna_fwimg.o
-
-EXTRA_CFLAGS := -Idrivers/net/bna