mm: mm_init: use div64_ul() instead of do_div()

Fixes Coccinelle/coccicheck warning reported by do_div.cocci.

Compared to do_div(), div64_ul() does not implicitly cast the divisor and
does not unnecessarily calculate the remainder.

There are no functional changes. The benefit is purely a semantic cleanup
that better communicates the intent of the division and resolves the
static analysis warning.

Signed-off-by: Giorgi Tchankvetadze <giorgitchankvetadze1997@gmail.com>
Link: https://patch.msgid.link/20260602-mm-div64-cleanup-v1-1-bf5d67d89d93@gmail.com
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>

Author: Giorgi Tchankvetadze

mm/mm_init.c

@@ -2412,7 +2412,7 @@ void *__init alloc_large_system_hash(const char *tablename,
 	/* limit allocation size to 1/16 total memory by default */
 	if (max == 0) {
 		max = ((unsigned long long)nr_all_pages << PAGE_SHIFT) >> 4;
-		do_div(max, bucketsize);
+		max = div64_ul(max, bucketsize);
 	}
 	max = min(max, 0x80000000ULL);