infra: remove usage of 4th parameter to inner-generic-package

In preparation of the removal of the 4th parameter to inner-generic-package
and the pkgparentdir helper function, this patch removes the direct usage of
this 4th parameter. The remaining usage
ifeq ($(4),boot/)
can become
$(filter boot/%,$(pkgdir))
instead (and similar for toolchain).

Signed-off-by: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/pkg-generic.mk

@@ -516,9 +516,9 @@ $$($(2)_TARGET_DIRCLEAN):		PKG=$(2)
 # kernel case, the bootloaders case, and the normal packages case.
 ifeq ($(1),linux)
 $(2)_KCONFIG_VAR = BR2_LINUX_KERNEL
-else ifeq ($(4),boot/)
+else ifneq ($(filter boot/%,$(pkgdir)),)
 $(2)_KCONFIG_VAR = BR2_TARGET_$(2)
-else ifeq ($(4),toolchain/)
+else ifneq ($(filter toolchain/%,$(pkgdir)),)
 $(2)_KCONFIG_VAR = BR2_$(2)
 else
 $(2)_KCONFIG_VAR = BR2_PACKAGE_$(2)