MIPS: tlb-r4k: Fix PG_ELPA comment

The ELPA bit in PageGrain is all about large *physical* addresses, so
correct the reference to "large virtual address" in the comment above
where it is set for MIPS64.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: David Daney <ddaney@caviumnetworks.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/10038/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>