valgrind: added perl dependency

valgrind: added perl dependency

This is necessary since the valgrind package depends on /usr/bin/perl.

This patch will fix this error while installing into rootfs:
Computing transaction...error: Can't install valgrind-3.8.1-r8@armv7a_vfp_neon: no package provides /usr/bin/perl

(From OE-Core rev: 9b21846ed8ae0fcd7b1d81d026cb03644ca7c1f7)

Signed-off-by: Felipe F. Tonello <eu@felipetonello.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>