[RenderScript] update the type of offsets for BLAS.BNNM

bug: 22184114

Change-Id: I7e7132aa3563f32de32640567b381f8f5bddf491
(cherry picked from commit 6099ee6e081904e73e0fad331e326b0607b6b1dc)
diff --git a/rs/jni/android_renderscript_RenderScript.cpp b/rs/jni/android_renderscript_RenderScript.cpp
index ec835b2..aac6c19 100644
--- a/rs/jni/android_renderscript_RenderScript.cpp
+++ b/rs/jni/android_renderscript_RenderScript.cpp
@@ -701,8 +701,8 @@
     call.M = M;
     call.N = N;
     call.K = K;
-    call.a_offset = a_offset;
-    call.b_offset = b_offset;
+    call.a_offset = a_offset & 0xFF;
+    call.b_offset = b_offset & 0xFF;
     call.c_offset = c_offset;
     call.c_mult_int = c_mult_int;