ARM: 6654/1: perf/oprofile: fix off-by-one in stack check

ARM: 6654/1: perf/oprofile: fix off-by-one in stack check

Since tail is the previous fp - 1, we need to compare the new fp with tail + 1
to ensure that we don't end up passing in the same tail again, in order to
avoid a potential infinite loop in the perf interrupt handler (which has been
observed to occur).  A similar fix seems to be needed in the OProfile code.

Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Rabin Vincent <rabin.vincent@stericsson.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>