graphics/khronos-texture: Turn off NEON for armv7 by default: the code uses intrinsics only available on aarch64

/wrkdirs/usr/ports/graphics/khronos-texture/work/KTX-Software-4.3.2/lib/astc-encoder/Source/astcenc_vecmathlib_neon_4.h:409:9: error: use of undeclared identifier 'vaddvq_u32'; did you mean 'vpaddlq_u32'?

409 |         return vaddvq_u32(vshlq_u32(tmp, shift));
    |                ^~~~~~~~~~
    |                vpaddlq_u32

/usr/lib/clang/19/include/arm_neon.h:21450:49: note: 'vpaddlq_u32' declared here
21450 | ai attribute((target("neon"))) uint64x2_t vpaddlq_u32(uint32x4_t p0) {

|                                                 ^

Same for: vminvq_s32 vmaxvq_s32 vqtbl1q_s8 vdivq_f32 vminnmq_f32
vmaxnmq_f32 vrndnq_f32 vminvq_f32 vmaxvq_f32 vsqrtq_f32 vcvt_f16_f32
vcvt_f32_f16 vqtbl1q_s8 vqtbl2q_s8 vaddvq_u32 vminvq_s32 vmaxvq_s32
vqtbl1q_s8 and etc.

https://portsfallout.com/fallout?port=graphics%2Fkhronos-texture