uma: Fix KMSAN integration with malloc zones

[markj]

Summary

In commit 459aa032e872 I dropped kmsan_mark() calls from malloc() on the
basis that UMA and kmem_malloc() would handle updates of the KMSAN
shadow map. However, I missed that UMA explicitly does not handle this.

Modify UMA to only omit origin map updates for malloc zones.

Fixes: 459aa032e872 ("malloc: Refactor redzone and sanitizer handling")

[rlibby]

Oops, I missed that too.