mm/gup_benchmark: update the documentation in Kconfig

In the beginning, mm/gup_benchmark.c supported get_user_pages_fast() only,
but right now, it supports the benchmarking of a couple of
get_user_pages() related calls like:

* get_user_pages_fast()
* get_user_pages()
* pin_user_pages_fast()
* pin_user_pages()

The documentation is confusing and needs update.
Signed-off-by: Barry Song <song.bao.hua@hisilicon.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Keith Busch <keith.busch@intel.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Link: https://lkml.kernel.org/r/20200821032546.19992-1-song.bao.hua@hisilicon.comSigned-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/Kconfig

@@ -831,10 +831,10 @@ config PERCPU_STATS
 	  be used to help understand percpu memory usage.
 
 config GUP_BENCHMARK
-	bool "Enable infrastructure for get_user_pages_fast() benchmarking"
+	bool "Enable infrastructure for get_user_pages() and related calls benchmarking"
 	help
 	  Provides /sys/kernel/debug/gup_benchmark that helps with testing
-	  performance of get_user_pages_fast().
+	  performance of get_user_pages() and related calls.
 
 	  See tools/testing/selftests/vm/gup_benchmark.c