Update ACL pin to b6869dda4a5bf233df009eaac15cf0c220b653f2
Update ACL pin to b6869dda4a5bf233df009eaac15cf0c220b653f2

Signed-off-by: Nikhil Raj <70dde441576cd8b053dd4c3a595f3f0b9c7a63a3@arm.com>
Change-Id: I1422eab2beb3d59841f827b60d822f987e08f326

ARM-software/armnn,ARM-software/armnn,ARM-software/armnn