MIPS: Yosemite, Emma: Fix off-by-two in arcs_cmdline buffer size check

Cause is a misplaced bracket.

The code

    strlen(buf+1)

will be two bytes less than

    strlen(buf)+1

The +1 is in this code to reserve space for an additional space character.

[ralf@linux-mips.org: Thomas' original patch fixed the issue only for
 Yosemite but the same bug exists also in Emma.]

Signed-off-by: Thomas Jarosch <thomas.jarosch@intra2net.com>
Patchwork: https://patchwork.linux-mips.org/patch/2861/


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