fix: consistently use constants instead of hardcoded numbers in unrolled BLAS loops

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---

Author: Planeshifter

lib/node_modules/@stdlib/blas/base/dcopy/src/dcopy_ndarray.c

@@ -55,11 +55,11 @@ void API_SUFFIX(c_dcopy_ndarray)( const CBLAS_INT N, const double *X, const CBLA
 				ix += strideX;
 				iy += strideY;
 			}
-			if ( N < 7 ) {
+			if ( N < M ) {
 				return;
 			}
 		}
-		for ( i = m; i < N; i += 7 ) {
+		for ( i = m; i < N; i += M ) {
 			Y[ iy ] = X[ ix ];
 			Y[ iy+1 ] = X[ ix+1 ];
 			Y[ iy+2 ] = X[ ix+2 ];

lib/node_modules/@stdlib/blas/base/sasum/src/sasum_ndarray.c

@@ -54,7 +54,7 @@ float API_SUFFIX(c_sasum_ndarray)( const CBLAS_INT N, const float *X, const CBLA
 				ix += stride;
 			}
 		}
-		if ( N < 6 ) {
+		if ( N < M ) {
 			return sum;
 		}
 		for ( i = m; i < N; i += M ) {

lib/node_modules/@stdlib/blas/base/scopy/src/scopy_ndarray.c

@@ -55,11 +55,11 @@ void API_SUFFIX(c_scopy_ndarray)( const CBLAS_INT N, const float *X, const CBLAS
 				ix += strideX;
 				iy += strideY;
 			}
-			if ( N < 7 ) {
+			if ( N < M ) {
 				return;
 			}
 		}
-		for ( i = m; i < N; i += 7 ) {
+		for ( i = m; i < N; i += M ) {
 			Y[ iy ] = X[ ix ];
 			Y[ iy+1 ] = X[ ix+1 ];
 			Y[ iy+2 ] = X[ ix+2 ];