sim: fix compilation on mingw64 [PR sim/28476]

...by reordering includes.

1. sim-utils.c

sim/mips/sim-main.h defines UserMode, while there is a struct in winnt.h
which has UserMode as a member. So if sim-main.h is included before winnt.h,
compilation fails.

2. ppc

registers.h defines CR, which is used as a member in winnt.h.

winsock2.h is included by sys/time.h, so sys/time.h has to be included
before registers.h.

Bug: https://sourceware.org/PR28476