selftests: lib.mk: Include test suite name in the RUN_TESTS output

Currently just the test name is printed in the RUN_TESTS output. For
example, when raw_skew sub-test from timers tests in run, the output
shows just raw_skew. Include main test name when printing sub-test
results.

In addition, remove duplicate strings for printing common information
with a new for the test header information.

Before the change:

selftests: raw_skew
========================================
WARNING: ADJ_OFFSET in progress, this will cause inaccurate results
Estimating clock drift: -20.616(est) -20.586(act)       [OK]
Pass 0 Fail 0 Xfail 0 Xpass 0 Skip 0 Error 0
1..0
ok 1..7 selftests: raw_skew [PASS]

After the change:

selftests: timers: raw_skew
========================================
WARNING: ADJ_OFFSET in progress, this will cause inaccurate results
Estimating clock drift: -19.794(est) -19.896(act)       [OK]
Pass 0 Fail 0 Xfail 0 Xpass 0 Skip 0 Error 0
1..0
ok 1..7 selftests: timers: raw_skew [PASS]

Signed-off-by: Shuah Khan (Samsung OSG) <shuah@kernel.org>