Get linux kernel version from Makefile of kernel source

We get below messages while building iscsitarget,

-- snip --
x86_64-poky-linux-gcc: error:
/CGE7_SHDD/project_yocto_1.8/poky/build/tmp/work-shared/qemux86-64/kernel-source/include/linux/version.h:
No such file or directory
x86_64-poky-linux-gcc: fatal error: no input files
compilation terminated.
/bin/sh: line 0: [: too many arguments
/bin/sh: line 0: [: too many arguments
/bin/sh: line 0: [: too many arguments
/bin/sh: line 0: [: too many arguments
/bin/sh: line 0: [: too many arguments
/bin/sh: line 0: [: too many arguments
/bin/sh: line 0: [: too many arguments
/bin/sh: line 0: [: too many arguments
/bin/sh: line 0: [: too many arguments
/bin/sh: line 0: [: too many arguments
/bin/sh: line 0: [: too many arguments
/bin/sh: line 0: [: too many arguments
-- CUT --

These messages are due to absence of include/linux/version.h file in 
kernel source directory and failed to compute linux kernel version.
So, use kernel source Makefile ( i.e $(KSRC)/Makefile) to find out 
actual kernel version.

Upstream-Status: Pending

Signed-off-by: Jagadeesh Krishnanjanappa <jkrishnanjanappa@mvista.com>

--- iscsitarget-1.4.20.3+svn499_org/Makefile	2014-01-27 00:00:45.000000000 +0530
+++ iscsitarget-1.4.20.3+svn499/Makefile	2015-07-23 10:44:47.013600285 +0530
@@ -18,27 +18,11 @@ ifeq ($(KSRC),)
 endif
 
 
-ifneq ($(wildcard $(KSRC)/include/generated/utsrelease.h),)
-	VERSION_FILE := $(KSRC)/include/generated/utsrelease.h
-else
-  ifneq ($(wildcard $(KSRC)/include/linux/utsrelease.h),)
-	  VERSION_FILE := $(KSRC)/include/linux/utsrelease.h
-  else
-	  VERSION_FILE := $(KSRC)/include/linux/version.h
-  endif
-endif
-
-KVER := $(shell $(CC) $(CFLAGS) $(LDFLAGS) -E -dM $(VERSION_FILE) | \
-	grep UTS_RELEASE | awk '{ print $$3 }' | sed 's/\"//g')
-
 KMOD := /lib/modules/$(KVER)/extra
-
-KMAJ := $(shell echo $(KVER) | \
-	sed -e 's/^\([0-9][0-9]*\)\.[0-9][0-9]*\.[0-9][0-9]*.*/\1/')
-KMIN := $(shell echo $(KVER) | \
-	sed -e 's/^[0-9][0-9]*\.\([0-9][0-9]*\)\.[0-9][0-9]*.*/\1/')
-KREV := $(shell echo $(KVER) | \
-	sed -e 's/^[0-9][0-9]*\.[0-9][0-9]*\.\([0-9][0-9]*\).*/\1/')
+KMAJ := $(shell cat $(KSRC)/Makefile | grep ^VERSION | gawk -F " " '{ print $$NF }')
+KMIN := $(shell cat $(KSRC)/Makefile | grep ^PATCHLEVEL | gawk -F " " '{ print $$NF }')
+KREV := $(shell cat $(KSRC)/Makefile | grep ^SUBLEVEL | gawk -F " " '{ print $$NF }')
+KVER := ${KMAJ}.${KMIN}.${KREV}
 
 kver_eq = $(shell [ $(KMAJ) -eq $(1) -a $(KMIN) -eq $(2) -a $(KREV) -eq $(3) ] && \
 	echo 1 || echo 0)