Mark parameter as [[maybe_unused]]

The width parameter is only used by some of the CPU-specific checks.
Add [[maybe_unused]] to fix the build for CPUs that do not vary the
implementation by width.

Fixes aosp_riscv64-userdebug build.

Test: builds
Change-Id: I0f69cf7cf4febc1ac16488633c2f5a997bdafc62
diff --git a/services/camera/libcameraservice/api2/HeicCompositeStream.cpp b/services/camera/libcameraservice/api2/HeicCompositeStream.cpp
index 71965f2..7a93cc7 100644
--- a/services/camera/libcameraservice/api2/HeicCompositeStream.cpp
+++ b/services/camera/libcameraservice/api2/HeicCompositeStream.cpp
@@ -1599,7 +1599,7 @@
     return OK;
 }
 
-void HeicCompositeStream::initCopyRowFunction(int32_t width)
+void HeicCompositeStream::initCopyRowFunction([[maybe_unused]] int32_t width)
 {
     using namespace libyuv;