ada: Enable checks during analysis of expanded dispatching calls

This patch enables the generation of run-time checks during the analysis and
resolution of expanded dispatching calls. They were previously disabled to avoid
reporting spurious warnings under the ZFP run-time, but this is no longer
required.

gcc/ada/ChangeLog:

	* exp_disp.adb (Expand_Dispatching_Call): Remove suppression of checks
	during analysis of expanded dispatching calls.