ada: exp_ch6.adb: entirely disable call validation in CodePeer_Mode

ada: exp_ch6.adb: entirely disable call validation in CodePeer_Mode

This call validation was introduced a couple of months ago and caused
GNAT2SCIL to fail a lot. It was determined that while being invalid for
GCC, the tree was valid for GNAT2SCIL. Since it was thought that only
the checking of the return type caused issue for CodePeer_Mode, this is
the only part that disabled. Recent changes revealed that there also
exists differences in the AST expected by GCC and GNAT2SCIL, and that
checking the actuals also causes issues for GNAT2SCIL. We hence entirely
disable the checking of calls in CodePeer_Mode instead of just the
checking of return values.

gcc/ada/ChangeLog:

	* exp_ch6.adb (Validate_Subprogram_Calls): Do not Check_Calls in CodePeer_Mode.
	(Check_Calls): Remove CodePeer_Mode special case.