MIPS: VDSO: Fix a mismatch between comment and preprocessor constant

MIPS: VDSO: Fix a mismatch between comment and preprocessor constant

Sync the comment with its preprocessor constant counterpart.

Signed-off-by: Aleksandar Markovic <aleksandar.markovic@imgtec.com>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: Miodrag Dinic <miodrag.dinic@imgtec.com>
Cc: Paul Burton <paul.burton@imgtec.com>
Cc: Petar Jovanovic <petar.jovanovic@imgtec.com>
Cc: Raghu Gandham <raghu.gandham@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/16641/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>