BC3-5: Remove potentially misaligned uint64 read
BC3-5: Remove potentially misaligned uint64 read

ARMv7 is fussy about this and explodes if src+2 isn't properly aligned,
which is likely to be the case.

VK-GL-CTS Issue: 954

Affects: dEQP-VK.texture.compressed.bc{3,4,5}*
Components: Framework

Change-Id: Idf0846603f4bf5d569a4084b8f399dd8da99221e
(cherry picked from commit f87519fd1d59e2c9beb06feeeae08c58fd8b9a51)

KhronosGroup/Vulkan-CTS,KhronosGroup/VK-GL-CTS,googlestadia/VK-GL-CTS,googlestadia/VK-GL-CTS,googlestadia/VK-GL-CTS,KhronosGroup/VK-GL-CTS,KhronosGroup/Vulkan-CTS,KhronosGroup/Vulkan-CTS,KhronosGroup/Vulkan-CTS,KhronosGroup/VK-GL-CTS,googlestadia/VK-GL-CTS,KhronosGroup/VK-GL-CTS,googlestadia/VK-GL-CTS,KhronosGroup/VK-GL-CTS,KhronosGroup/Vulkan-CTS,KhronosGroup/VK-GL-CTS,googlestadia/VK-GL-CTS,KhronosGroup/Vulkan-CTS