crt: Use __p__commode instead of __MINGW_IMP_SYMBOL(_commode) for initialization

This matches what was done for _fmode in
2e64b9e4537d564478f17b873b2f655f518325ed. This fixes using a
crtexe.c built without optimizations with UCRT (and fixes UCRT
in general after the previous commit).

Signed-off-by: Martin Storsjö <martin@martin.st>