memory_block may have a larger granularity than section, this is why we
have base_section_nr. But base_memory_block_id seems a little
misleading, since there is no larger granularity concept which groups
several memory_block.

What we need here is the exact memory_block_id to a section_nr. Let's
rename it to make it more precise.
Signed-off-by: Wei Yang <richard.weiyang@linux.alibaba.com>
Link: https://lore.kernel.org/r/20200623025701.2016-2-richard.weiyang@linux.alibaba.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>