samples/bpf: README: Update build dependencies required

Update samples/bpf/README.rst to add pahole to the build dependencies
list. Add the reference to "Documentation/process/changes.rst" for
minimum version required so that the version required will not be
outdated in the future.

Signed-off-by: Anh Tuan Phan <tuananhlfc@gmail.com>
Link: https://lore.kernel.org/r/aecaf7a2-9100-cd5b-5cf4-91e5dbb2c90d@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

samples/bpf/README.rst

@@ -8,11 +8,14 @@ Build dependencies
 ==================
 
 Compiling requires having installed:
- * clang >= version 3.4.0
- * llvm >= version 3.7.1
+ * clang
+ * llvm
+ * pahole
 
-Note that LLVM's tool 'llc' must support target 'bpf', list version
-and supported targets with command: ``llc --version``
+Consult :ref:`Documentation/process/changes.rst <changes>` for the minimum
+version numbers required and how to update them. Note that LLVM's tool
+'llc' must support target 'bpf', list version and supported targets with
+command: ``llc --version``
 
 Clean and configuration
 -----------------------
@@ -24,7 +27,8 @@ after some changes (on demand)::
  make -C samples/bpf clean
  make clean
 
-Configure kernel, defconfig for instance::
+Configure kernel, defconfig for instance
+(see "tools/testing/selftests/bpf/config" for a reference config)::
 
  make defconfig