Do not crash when asking ix86_widen_mult_cost for the cost of
a widening mul operation to V4HI or V2SImode.

gcc/ChangeLog:

    PR target/109807
    * config/i386/i386.cc (ix86_widen_mult_cost):
    Handle V4HImode and V2SImode.

gcc/testsuite/ChangeLog:

    PR target/109807
    * gcc.target/i386/pr109807.c: New test.

Bootstrapped and regression tested on x86_64-linux-gnu {,-m32}.

Pushed to master.

Uros.