valgrind: Enable valgrind for armv7

valgrind: Enable valgrind for armv7

Valgrind supports the armv7 architecture, this patch allows armv7 users to build and use Valgrind

This patch was run-tested on a Gumstix Overo (armv7a cortex-a8)
* The test consisted of running valgrinds memcheck (memory leakage detection),
* and callgrind (profiling) on a Qt 4 application

(From OE-Core rev: 211ac8b39023d4998fb7d5a577b63a4960b08172)

Signed-off-by: Samuel Stirtzel <s.stirtzel@googlemail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>