wasm: mark freeJSVal as INLINE

This patch marks `freeJSVal` as `INLINE` for the wasm backend. I
noticed that the `freeJSVal` invocations are not inlined when
inspecting STG/Cmm dumps of downstream libraries that use release
build of the wasm backend. The performance benefit of inlining here is
very modest, but so is the cost anyway; if you are using `freeJSVal`
at all then you care about every potential chance to improve
performance :)

libraries/ghc-internal/src/GHC/Internal/Wasm/Prim/Types.hs

@@ -147,6 +147,7 @@ data JSVal
 -- the same 'JSVal', subsequent invocations are no-ops. You are
 -- strongly recommended to call 'freeJSVal' on short-lived
 -- intermediate 'JSVal' values for timely release of resources!
+{-# INLINE freeJSVal #-}
 freeJSVal :: JSVal -> IO ()
 freeJSVal v@(JSVal p) = do
   js_callback_unregister v