[openrisc] Patch for correctiong timeout interrupt

[Carlos Sánchez de La Lama <csanchez@teisa.unican.es>]

Here is the patch. I also send a patch to make PICSR bit assigned to
UART to go back to 0 when UART interrupt line is deasserted, in case it
is finaly decided it to work this way.

Regards,

	Carlos
549c552,553
<       && (uarts[i].istat.timeout_count >= UART_CHAR_TIMEOUT * uarts[i].char_clks)) {
---
>       && (uarts[i].istat.timeout_count >= UART_CHAR_TIMEOUT * uarts[i].char_clks)
>       && (uarts[i].istat.rxbuf_head != uarts[i].istat.rxbuf_tail)) {
41a42,44
> #include "spr_defs.h"
> #include "sprs.h"
> 
563a567
>   else setsprbit(SPR_PICSR, config.uarts[i].irq, 0);

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