kirkwood: add generic subtarget

Same game as for 853e4dd3062df7cb5704b15d6af6730e3194b571. Add generic
to the filenames.

Signed-off-by: Christian Marangi <[email protected]>

target/linux/kirkwood/Makefile

@@ -9,6 +9,7 @@ BOARD:=kirkwood
 BOARDNAME:=Marvell Kirkwood
 FEATURES:=usb nand squashfs ramdisk
 CPU_TYPE:=xscale
+SUBTARGETS:=generic
 
 KERNEL_PATCHVER:=5.10
 KERNEL_TESTING_PATCHVER:=5.15

target/linux/kirkwood/generic/target.mk

@@ -0,0 +1 @@
+BOARDNAME:=Generic