arm: rmobile: Fix off-by-one error in cpuinfo

In rmobile_cpuinfo_idx() there is an off-by-one error in accessing the
rmobile_cpuinfo array.

At the end of the loop, i is equal to the array size, i.e.
rmobile_cpuinfo[i] accesses one entry past the end of the array. The
last entry in the array is a fallback value so the loop should count to
ARRAY_SIZE(rmobile_cpuinfo) - 1 instead, this will leave i equal to the
index of the fallback value if no match is found.

Signed-off-by: Paul Barker <paul.barker.ct@bp.renesas.com>
Reviewed-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Marek Vasut <marek.vasut+renesas@mailbox.org>