mapper: update documentation on locking

Update the locking documentation to require all 1D buffers
"lock in place". Previously, the framework was able to get 1D
buffers that locked in place via ion. The ion interface is no
longer directly accessible. Some framework use cases still need
1D buffers that lock in place so add the requirement to mapper.

Bug: 120493579
Test: N/A
Change-Id: Ib903efdbeeb8c44ed70c3c6022d6792d05df1a63

graphics/mapper/3.0/IMapper.hal

@@ -183,6 +183,9 @@ interface IMapper {
      * buffer content in an indeterminate state or returning an error are both
      * acceptable.
      *
+     * 1D buffers (width = size in bytes, height = 1, pixel_format = BLOB) must
+     * "lock in place". The buffers must be directly accessible via mapping.
+     *
      * The client must not modify the content of the buffer outside of
      * @p accessRegion, and the device need not guarantee that content outside
      * of @p accessRegion is valid for reading. The result of reading or writing