qemu-log: Remove qemu_log_try_set_file() and its users

Remove the function qemu_log_try_set_file() and its users (which
are all in TCG code generation functions for various targets).
This function was added to abstract out code which was originally
written as "if (!logfile) logfile = stderr;" in order that BUG:
case code which did an unguarded "fprintf(logfile, ...)" would
not crash if debug logging was not enabled. Since those direct
uses of logfile have also been abstracted away into qemu_log()
calls which check for a NULL logfile, there is no need for the
target-* files to mess with the user's chosen logging settings.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Andreas Färber <afaerber@suse.de>
Acked-by: Michael Walle <michael@walle.cc>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
