x86: mm: refer to the intended config STRICT_DEVMEM in a comment

Commit a4866aa ("mm: Tighten x86 /dev/mem with zeroing reads") adds a
comment to the function devmem_is_allowed() referring to a non-existing
config STRICT_IOMEM, whereas the comment very likely intended to refer to
the config STRICT_DEVMEM, as the commit adds some behavior for the config
STRICT_DEVMEM.

Most of the initial analysis was actually done by Dave Hansen in the
email thread below (see Link).

Refer to the intended and existing config STRICT_DEVMEM.

Link: https://lore.kernel.org/r/[email protected]/

Suggested-by: Dave Hansen <[email protected]>
Signed-off-by: Lukas Bulwahn <[email protected]>
Signed-off-by: Kees Cook <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: bulwahn

arch/x86/mm/init.c

@@ -846,7 +846,7 @@ int devmem_is_allowed(unsigned long pagenr)
 
 	/*
 	 * This must follow RAM test, since System RAM is considered a
-	 * restricted resource under CONFIG_STRICT_IOMEM.
+	 * restricted resource under CONFIG_STRICT_DEVMEM.
 	 */
 	if (iomem_is_exclusive(pagenr << PAGE_SHIFT)) {
 		/* Low 1MB bypasses iomem restrictions. */