The v850 family contains several related-but-not-identical on-chip
UARTs.  This patch factors out the common code and uses it to implement
both types (only one was supported before).

Also, this patch changes the way the v850 UART is initialized, to use
the same method as other linux serial drivers.

This patch renames the UART code to be `v850e_uart' rather than
`nb85e_uart', as the former is more correct.  As this change renames
some files too, the patch contains a number of whole-file add/removes.