cmd/compile: fix lineno restoration after SSA compilation

Without SSA:

$ go build -a -gcflags='-S -ssa=0' runtime 2>&1 | grep 'TEXT.*""\.init(SB)'
        0x0000 00000 ($GOROOT/src/runtime/write_err.go:14)        TEXT    "".init(SB), $88-0

With SSA, before this CL:

$ go build -a -gcflags='-S -ssa=1' runtime 2>&1 | grep 'TEXT.*""\.init(SB)'
        0x0000 00000 ($GOROOT/src/runtime/traceback.go:608)       TEXT    "".init(SB), $152-0

With SSA, after this CL:

$ go build -a -gcflags='-S -ssa=1' runtime 2>&1 | grep 'TEXT.*""\.init(SB)'
        0x0000 00000 ($GOROOT/src/runtime/write_err.go:14)        TEXT    "".init(SB), $152-0

Change-Id: Ida3541e03a1af6ffc753ee5c3abeb653459edbf6
Reviewed-on: https://go-review.googlesource.com/20321
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

src/cmd/compile/internal/gc/pgen.go

@@ -484,11 +484,8 @@ func compile(fn *Node) {
 
 	if ssafn != nil {
 		genssa(ssafn, ptxt, gcargs, gclocals)
-		if Curfn.Func.Endlineno != 0 {
-			lineno = Curfn.Func.Endlineno
-		}
 		ssafn.Free()
-		return
+		goto ret
 	}
 	Genlist(Curfn.Func.Enter)
 	Genlist(Curfn.Nbody)