Merge pull request opencv#18228 from joy2myself:rvv

Author: vpisarev

modules/core/include/opencv2/core/cv_cpu_dispatch.h

@@ -170,6 +170,7 @@
 
 #if defined CV_CPU_COMPILE_RVV
 #  define CV_RVV 1
+#  include <riscv_vector.h>
 #endif
 
 #endif // CV_ENABLE_INTRINSICS && !CV_DISABLE_OPTIMIZATION && !__CUDACC__

modules/core/include/opencv2/core/hal/intrin.hpp

@@ -202,7 +202,7 @@ using namespace CV_CPU_OPTIMIZATION_HAL_NAMESPACE;
 #   undef CV_RVV
 #endif
 
-#if (CV_SSE2 || CV_NEON || CV_VSX || CV_MSA || CV_WASM_SIMD) && !defined(CV_FORCE_SIMD128_CPP)
+#if (CV_SSE2 || CV_NEON || CV_VSX || CV_MSA || CV_WASM_SIMD || CV_RVV) && !defined(CV_FORCE_SIMD128_CPP)
 #define CV__SIMD_FORWARD 128
 #include "opencv2/core/hal/intrin_forward.hpp"
 #endif