hw/arm/exynos4210: fix Exynos4210 UART support

hw/arm/exynos4210: fix Exynos4210 UART support

commit 97274d0c05d4 ("hw/char/exynos4210_uart.c: Remove unneeded
handling of NULL chardev") broke Exynos4210 support as it removed
NULL 'Chardev *chr' handling from exynos4210_uart_create() and
currently exynos4210_init() always passes NULL as 'Chardev *chr'
argument to exynos4210_uart_create() calls. Fix it by adding
missing serial_hd() calls to exynos4210_init().

Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 9310418.Wg32kryeWE@amdc3058
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>