lib/test_free_pages.c: add basic progress indicators

lib/test_free_pages.c: add basic progress indicators

The test module to check that free_pages() does not leak memory does not
provide any feedback whatsoever its state or progress, but may take some
time on slow machines.  Add the printing of messages upon starting each
phase of the test, and upon completion.

Link: https://lkml.kernel.org/r/20201018140445.20972-1-geert@linux-m68k.org
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>