perf check-headers.sh: Add support to check 2 independent files

Add 'check_2' function to check 2 different files, the 'check' function
stays to check files that differs only in the prefix path.

In upcoming changes we need to check header files in locations which
don't follow the prefix logic.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20180423090823.32309-3-jolsa@kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/check-headers.sh

@@ -55,17 +55,26 @@ include/uapi/asm-generic/ioctls.h
 include/uapi/asm-generic/mman-common.h
 '
 
-check () {
-  file=$1
+check_2 () {
+  file1=$1
+  file2=$2
 
+  shift
   shift
 
-  cmd="diff $* ../$file ../../$file > /dev/null"
+  cmd="diff $* $file1 $file2 > /dev/null"
 
-  test -f ../../$file &&
+  test -f $file2 &&
   eval $cmd || echo "Warning: Kernel ABI header at 'tools/$file' differs from latest version at '$file'" >&2
 }
 
+check () {
+  file=$1
+
+  shift
+
+  check_2 ../$file ../../$file $*
+}
 
 # Check if we have the kernel headers (tools/perf/../../include), else
 # we're probably on a detached tarball, so no point in trying to check