Add dg-require-profiling directives to gcc.target/i386 tests

This patch adds /* { dg-require-profiling "-pg" } */
to a few tests in gcc.target/i386 that use -pg explicitly, to
prevent them from failing during runs for VxWorks targets.

2020-10-29  Olivier Hainque  <hainque@adacore.com>

gcc/testsuite/
	* gcc.target/i386/fentryname1.c: Add dg-require-profiling.
	* gcc.target/i386/fentryname2.c: Likewise.
	* gcc.target/i386/fentryname3.c: Likewise.
	* gcc.target/i386/returninst1.c: Likewise.
	* gcc.target/i386/returninst2.c: Likewise.
	* gcc.target/i386/returninst3.c: Likewise.