i386: Handle unsupported modes from ix86_widen_mult_cost [PR109807]

i386: Handle unsupported modes from ix86_widen_mult_cost [PR109807]

Revert my previous change that faked handling of V4HI and V2SImodes
in ix86_widen_mult_cost and rather return arbitrary high value
for unsupported modes. This should prevent cost estimator from
selecting non-existent vector widen multiply operation.

gcc/ChangeLog:

	PR target/109807
	* config/i386/i386.cc: Revert the 2023-05-11 change.
	(ix86_widen_mult_cost): Return high value instead of
	ICEing for unsupported modes.

gcc/testsuite/ChangeLog:

	PR target/109807
	* gcc.target/i386/pr109825.c: New test.