The previous code dereferenced a uint32_t * that might be misaligned,
which is technically undefined behaviour in C. This version uses the
right (cryptically named) Intel intrinsics to generate a MOVD without
making any claims about the alignment of the pointer.

BUG=aomedia:912

Change-Id: Ic51679b9f9ed4d2476e69da70f40b2d599cbc6b0