ramips: switch rt305x subtarget to kernel 5.4

RT3x5x seems to work fine with kernel 5.4. Set the default kernel
version to 5.4 to bring this to a broader audience.

Since 4 of 6 targets are on kernel 5.4 now, invert the kernel
version setup logic in Makefile/target.mk files.

Tested on ZyXEL Keenetic.

Signed-off-by: Alexey Dobrovolsky <dobrovolskiy.alexey@gmail.com>
[invert version setup logic]
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>

target/linux/ramips/Makefile

@@ -12,7 +12,7 @@ BOARDNAME:=MediaTek Ralink MIPS
 SUBTARGETS:=mt7620 mt7621 mt76x8 rt288x rt305x rt3883
 FEATURES:=squashfs gpio
 
-KERNEL_PATCHVER:=4.14
+KERNEL_PATCHVER:=5.4
 KERNEL_TESTING_PATCHVER:=5.4
 
 define Target/Description

target/linux/ramips/mt7620/target.mk

@@ -9,8 +9,6 @@ CPU_TYPE:=24kc
 
 DEFAULT_PACKAGES += kmod-rt2800-soc wpad-basic swconfig
 
-KERNEL_PATCHVER:=5.4
-
 define Target/Description
 	Build firmware images for Ralink MT7620 based boards.
 endef

target/linux/ramips/mt7621/target.mk

@@ -7,8 +7,6 @@ BOARDNAME:=MT7621 based boards
 FEATURES+=nand ramdisk rtc usb minor
 CPU_TYPE:=24kc
 
-KERNEL_PATCHVER:=5.4
-
 define Target/Description
 	Build firmware images for Ralink MT7621 based boards.
 endef

target/linux/ramips/mt76x8/target.mk

@@ -8,7 +8,6 @@ FEATURES+=usb ramdisk
 CPU_TYPE:=24kc
 
 DEFAULT_PACKAGES += kmod-mt7603 wpad-basic swconfig
-KERNEL_PATCHVER:=5.4
 
 define Target/Description
 	Build firmware images for Ralink MT76x8 based boards.

target/linux/ramips/rt288x/target.mk

@@ -9,6 +9,8 @@ CPU_TYPE:=24kc
 
 DEFAULT_PACKAGES += kmod-rt2800-soc wpad-mini swconfig
 
+KERNEL_PATCHVER:=4.14
+
 define Target/Description
 	Build firmware images for Ralink RT288x based boards.
 endef

target/linux/ramips/rt3883/target.mk

@@ -9,6 +9,8 @@ CPU_TYPE:=74kc
 
 DEFAULT_PACKAGES += kmod-rt2800-pci kmod-rt2800-soc wpad-mini swconfig
 
+KERNEL_PATCHVER:=4.14
+
 define Target/Description
 	Build firmware images for Ralink RT3662/RT3883 based boards.
 endef