kernel/wasm/KERNEL is included after KERNEL.WASM128_GENERIC and
unconditionally pointed S/D AXPY at RISC-V scalar axpy.c, so the
x86_64 V_SIMD sources listed in the target file never ran.
Add kernel/wasm/axpy.c for both precisions. Unit-stride y += da * x
uses eight independent v128 lanes (32 floats / 16 doubles) with IEEE
mul+add; remainder is one vector then scalar. Skip relaxed madd:
AXPY is checked to machine epsilon, and putting it in the generic
V_SIMD path previously slowed Level 1. Non-unit stride stays scalar
(no WASM gather); inc==0 uses that path so y[0] += n * da * x[0].
Guard SAXPYKERNEL/DAXPYKERNEL with ifndef in KERNEL so the target
file wins. CAXPY/ZAXPY stay RISC-V scalar.
On n=512..8192 vs the RISC-V champion, SAXPY is about 1.4–3.0x and
DAXPY about 1.4–2.2x. test.sh is green.
Signed-off-by: Julien Jerphanion <git@jjerphan.xyz>
