exynos4210_uart.c: SIGSEGV when loadvm
Description of problem:
Line 619 of hw/char/exynos4210_uart.c cast the object incorrectly.

The function will be called with Exynos4210UartFIFO as opaque because it is set as `vmstate_exynos4210_uart_fifo.post_load`

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Steps to reproduce:
1. Create a VM with exynos4210_uart
2. savevm 
3. loadvm
Additional information: