graphics/gdal: fix build on armv7

This port uses NEON through the sse2neon.h header.  Unfortunately the
header is written such that there is no difference between __m128 and
__m128d, while real SSE intrinsics have such a difference.  This causes
problems with some template functions down the road.

Disable NEON on armv7 to avoid this problem.

Approved by:	portmgr (build fix blanket)
MFH:		2025Q3