semihosting: fix order of initialization functions
qemu_semihosting_console_init uses semihosting.chardev which is set
by qemu_semihosting_connect_chardevs. Thus qemu_semihosting_connect_chardevs
has to be called first.
Both have to be called after processing -serial and friends though, so
that the semihosting console can connect to a multiplexer as in
"-serial mon:stdio -semihosting-config chardev=serial0"