x86: fix condition in base-files.mk

TARGET_x86_generic_Soekris48xx is not defined,
CONFIG_TARGET_x86_generic_Soekris48xx is

This changes makes it possible to override the network config for soekris net48xx
and net45xx targets.

Signed-off-by: Bruno Randolf <br1@einfach.org>

SVN-Revision: 38450

target/linux/x86/base-files.mk

-ifneq ($(TARGET_x86_generic_Soekris48xx)$(TARGET_x86_generic_Soekris45xx),)
+ifneq ($(CONFIG_TARGET_x86_generic_Soekris48xx)$(CONFIG_TARGET_x86_generic_Soekris45xx),)
 define Package/base-files/install-target
 	rm -f $(1)/etc/config/network
 endef