Hi,

The 'vect_recog_bitfield_ref_pattern' was not correctly adapting the 
vectype when widening the container.

I thought the original tests covered that code-path but they didn't, so 
I added a new run-test that covers it too.

Bootstrapped and regression tested on x86_64 and aarch64.

gcc/ChangeLog:

     PR tree-optimization/107326
     * tree-vect-patterns.cc (vect_recog_bitfield_ref_pattern): Change
     vectype when widening container.

gcc/testsuite/ChangeLog:

     * gcc.dg/vect/pr107326.c: New test.
     * gcc.dg/vect/vect-bitfield-read-7.c