internal/syscall/unix: implement randomTrap on mips64p32*

    
    Rename getrandom_linux_mipsn32.go to use the new architecture name for
    the n32 ABI and enable building it on mips64p32 and mips64p32le.
    
    Reviewed-on: https://go-review.googlesource.com/46151

From-SVN: r249474

gcc/go/gofrontend/MERGE

-b2bebba1f8a8185546c47f8460a3d5c2e31d0434
+c49c752b4d2934cff325dd540821c4b27cc61a05
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

libgo/go/internal/syscall/unix/getrandom_linux_mipsn32.go → libgo/go/internal/syscall/unix/getrandom_linux_mips64p32x.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build mipsn32
+// +build mipsn32 mips64p32 mips64p32le
 
 package unix