Documentation: kselftests: Remove references to bpf tests

Currently the bpf selftests are skipped by default, so is someone would
like to run the tests one would need to run:
  $ make TARGETS=bpf SKIP_TARGETS="" kselftest

To overwrite the SKIP_TARGETS that defines bpf by default. Also,
following the BPF instructions[1], to run the bpf selftests one would
need to enter in the tools/testing/selftests/bpf/ directory, and then
run make, which is not the standard way to run selftests per it's
documentation.

For the reasons above stop mentioning bpf in the kselftests as examples
of how to run a test suite.

[1]: Documentation/bpf/bpf_devel_QA.rst
Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

Documentation/dev-tools/kselftest.rst

@@ -112,7 +112,7 @@ You can specify multiple tests to skip::
 You can also specify a restricted list of tests to run together with a
 dedicated skiplist::
 
-  $  make TARGETS="bpf breakpoints size timers" SKIP_TARGETS=bpf kselftest
+  $  make TARGETS="breakpoints size timers" SKIP_TARGETS=size kselftest
 
 See the top-level tools/testing/selftests/Makefile for the list of all
 possible targets.
@@ -165,7 +165,7 @@ To see the list of available tests, the `-l` option can be used::
 The `-c` option can be used to run all the tests from a test collection, or
 the `-t` option for specific single tests. Either can be used multiple times::
 
-   $ ./run_kselftest.sh -c bpf -c seccomp -t timers:posix_timers -t timer:nanosleep
+   $ ./run_kselftest.sh -c size -c seccomp -t timers:posix_timers -t timer:nanosleep
 
 For other features see the script usage output, seen with the `-h` option.
 
@@ -210,7 +210,7 @@ option is supported, such as::
 tests by using variables specified in `Running a subset of selftests`_
 section::
 
-    $ make -C tools/testing/selftests gen_tar TARGETS="bpf" FORMAT=.xz
+    $ make -C tools/testing/selftests gen_tar TARGETS="size" FORMAT=.xz
 
 .. _tar's auto-compress: https://www.gnu.org/software/tar/manual/html_node/gzip.html#auto_002dcompress