tests/memrange-test: Correct commentary on test_memrange_steal()

Currently, memranges_steal() steals at the lowest possible address.
This is actually reflected by the test code that checks if the *base*
of the READONLY_TAG range changes. Furthermore, the test ends with the
memranges restored, so revise the comment on the final state.

Change-Id: Idef71ce464280c6805145f229de9e8913ba850bc
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/66606
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-by: Jan Dabros <jsd@semihalf.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

tests/lib/memrange-test.c

@@ -461,7 +461,7 @@ static void test_memrange_holes(void **state)
  * memory from region with READONLY_TAG.
  *
  * Example memory ranges (res_mock1) for test_memrange_steal.
- * Space marked with (/) is not covered by any region at the end of the test.
+ * Space marked with (/) is stolen during the test.
  *
  *     +--------CACHEABLE_TAG--------+ <-0xE000
  *     |                             |
@@ -471,10 +471,10 @@ static void test_memrange_holes(void **state)
  *
  *
  *
- *     +--------READONLY_TAG---------+ <-0xFF0000
- *     |                             |
- *     |/////////////////////////////| <-stolen_base
+ *     +--------READONLY_TAG---------+ <-0xFF0000  <-stolen_base
  *     |/////////////////////////////|             <-stolen_base + 0x4000
+ *     |                             |
+ *     |                             |
  *     +-----------------------------+ <-0x1000000
  *
  *