mm/sparse: remove unnecessary NULL check before allocating mem_section

mm/sparse: remove unnecessary NULL check before allocating mem_section

Commit 850ed20539a4 ("mm: move array mem_section init code out of
memory_present()") moved mem_section allocation logic into
memblocks_present().

Before that move, memory_present() could be called multiple times, so
unlikely() matched the common case, where most calls found mem_section
already allocated.

After that move, memblocks_present() is called exactly once from
sparse_init().  Under CONFIG_SPARSEMEM_EXTREME, mem_section is always NULL
when it is called.

So remove unnecessary NULL check before allocating mem_section.  No
functional change.

Link: https://lore.kernel.org/20260419144225.2875654-1-ekffu200098@gmail.com
Signed-off-by: Sang-Heon Jeon <ekffu200098@gmail.com>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed by: Donet Tom <donettom@linux.ibm.com>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Cc: Liam Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>