mm: drop duplicated words in <linux/pgtable.h>

Drop the doubled words "used" and "by".

Drop the repeated acronym "TLB" and make several other fixes around it.
(capital letters, spellos)

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: SeongJae Park <sjpark@amazon.de>
Link: http://lkml.kernel.org/r/2bb6e13e-44df-4920-52d9-4d3539945f73@infradead.org


Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>