ui/console: remove console_ch_t typedef and console_write_ch()

Since commit e2f82e924d05 ("console: purge curses bits from
console.h"), console_ch_t is a plain uint32_t typedef and
console_write_ch() is a trivial assignment (*dest = ch). These
abstractions were originally needed because console_ch_t was the
curses chtype when CONFIG_CURSES was enabled, and console_write_ch()
handled VGA-to-curses character translation. That commit moved the
curses logic into curses_update(), making the typedef and helper
dead abstractions.

Replace console_ch_t with uint32_t and console_write_ch() calls
with direct assignments.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>