mm/memblock.c: remove redundant assignment to variable max_addr

mm/memblock.c: remove redundant assignment to variable max_addr

The variable max_addr is being initialized with a value that is never read
and it is being updated later with a new value.  The initialization is
redundant and can be removed.

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>
Link: http://lkml.kernel.org/r/20200228235003.112718-1-colin.king@canonical.com
Addresses-Coverity: ("Unused value")
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>