realtek: remove KERNEL_PATCHVER overrides

On the realtek target, the subtarget makefiles include a KERNEL_PATCHVER
setting, shadowing KERNEL_PATCHVER from target/linux/realtek/Makefile.
This makes the realtek target an exception in this regard, and makes
switching kernel version a bit bothersome. Remove the overrides so all
subtargets use the same kernel version.

Signed-off-by: Sander Vanheule <[email protected]>

target/linux/realtek/rtl838x/target.mk

@@ -5,8 +5,6 @@ CPU_TYPE:=4kec
 BOARD:=realtek
 BOARDNAME:=Realtek MIPS RTL838X
 
-KERNEL_PATCHVER:=5.10
-
 define Target/Description
 	Build firmware images for Realtek RTL838x based boards.
 endef

target/linux/realtek/rtl839x/target.mk

@@ -5,8 +5,6 @@ CPU_TYPE:=24kc
 BOARD:=realtek
 BOARDNAME:=Realtek MIPS RTL839X
 
-KERNEL_PATCHVER:=5.10
-
 define Target/Description
 	Build firmware images for Realtek RTL839x based boards.
 endef

target/linux/realtek/rtl930x/target.mk

@@ -5,8 +5,6 @@ CPU_TYPE:=24kc
 BOARD:=realtek
 BOARDNAME:=Realtek MIPS RTL930X
 
-KERNEL_PATCHVER:=5.10
-
 define Target/Description
 	Build firmware images for Realtek RTL930x based boards.
 endef

target/linux/realtek/rtl931x/target.mk

@@ -5,8 +5,6 @@ CPU_TYPE:=24kc
 BOARD:=realtek
 BOARDNAME:=Realtek MIPS RTL931X
 
-KERNEL_PATCHVER:=5.10
-
 define Target/Description
 	Build firmware images for Realtek RTL931x based boards.
 endef