[Ada] Fix scope of block in expanded protected entry body

[Ada] Fix scope of block in expanded protected entry body

We expand protected entry body into procedure with a nested block. The
scope of this block is naturally the enclosing procedure. However, the
scope field was wrongly set to the entity of the enclosing procedure
body (i.e. E_Subprogram_Body); now it is set to the entity of the
enclosing procedure spec (i.e. E_Procedure).

In general, the scope field should always points to spec, even for
entities that are syntactically nested within a program unit body. The
scope set to E_Subprogram_Body entity was only accepted because in gigi
we had a protection for that, but this protection is now removed.

This patch fixes a regression in a ravenscar testsuite test (c_rf02_06),
where GNAT was crashing when compiling in configurable runtime mode with
restriction No_Exception_Propagation.

gcc/ada/

	* exp_ch9.adb (Build_Protected_Entry): Set scope of the nested
	block to spec and not the body of the procedure created for a
	protected entry.