kernel: Restore TARGET_KERNEL_VERSION

#   TARGET_KERNEL_LLVM_BINUTILS        = Use LLVM binutils, defaults to true

#   TARGET_KERNEL_NO_GCC               = Fully compile the kernel without GCC.

#                                        Defaults to false

#   TARGET_KERNEL_VERSION              = Reported kernel version in top level kernel

#                                        makefile. Can be overriden in device trees

#                                        in the event of prebuilt kernel.

#

#   TARGET_KERNEL_DTBO_PREFIX          = Override path prefix of TARGET_KERNEL_DTBO.

#                                        Defaults to empty

KERNEL_VERSION := $(shell grep -s "^VERSION = " $(TARGET_KERNEL_SOURCE)/Makefile | awk '{ print $$3 }')

KERNEL_PATCHLEVEL := $(shell grep -s "^PATCHLEVEL = " $(TARGET_KERNEL_SOURCE)/Makefile | awk '{ print $$3 }')

TARGET_KERNEL_VERSION ?= $(shell echo $(KERNEL_VERSION)"."$(KERNEL_PATCHLEVEL))

# 5.10+ can fully compile without GCC by default

ifeq ($(shell expr $(KERNEL_VERSION) \>= 5), 1)