cgen: peel *fn field types for local struct-field callees

fnptrcalleetfn's N_DOT arm accepted only a bare N_TFN field tnode, so
a call through a field declared `cb: *fn(...)` missed, fell through to
the name registry, and emitted CALL cb(SB) — an undefined symbol
(loud at link; cstage calls the stamped ptr-to-fn indirectly). Same
TPTR peel the N_IDENT arm already had. Fixture fnptrfield_call covers
the by-value and via-pointer shapes; corpus pin 1478/2956.

internal/wwfixture/types.ww

@@ -1,13 +1,13 @@
 package wwfixture;
 
 def protocolversion: i32 = 1;
-def corpuscount: i32 = 1477;
+def corpuscount: i32 = 1478;
 def errorcount: i32 = 335;
 def compilecount: i32 = 17;
 def runcount: i32 = 191;
-def runexitcount: i32 = 934;
-def nativecount: i32 = 2954;
-def corpushash: str = "64258f4de9ac7d71c4ad6221dd2ae7338a38cd5c620fc4ce22c1105021559e83";
+def runexitcount: i32 = 935;
+def nativecount: i32 = 2956;
+def corpushash: str = "2ac2342a80c4148968250bf4ce93852b78cdefb6af96622fa533eea4a68837c6";
 
 type directive = enum i32 {
 	ERROR = 0,