mm: fix typos in comments

Fix ~94 single-word typos in locking code comments, plus a few
very obvious grammar mistakes.

Link: https://lkml.kernel.org/r/20210322212624.GA1963421@gmail.com
Link: https://lore.kernel.org/r/20210322205203.GB1959563@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Bhaskar Chowdhury <unixbhaskar@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/highmem.c b/mm/highmem.c
index e389337..4fb51d7 100644
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -519,7 +519,7 @@ void *__kmap_local_pfn_prot(unsigned long pfn, pgprot_t prot)
 
 	/*
 	 * Disable migration so resulting virtual address is stable
-	 * accross preemption.
+	 * across preemption.
 	 */
 	migrate_disable();
 	preempt_disable();