[SERIAL] Fix /proc serial info for MMIO ports

[SERIAL] Fix /proc serial info for MMIO ports

Patch from: Bjorn Helgaas

This patch against 2.6.2 fixes a minor issue with /proc/tty/drivers/*,
which currently doesn't show MMIO address information.  Current
sample output:

        # cat /proc/tty/driver/serial
        serinfo:1.0 driver revision:
        0: uart:16450 port:00000000 irq:65 tx:72 rx:0 RTS|DTR
        1: uart:16550A port:00000000 irq:65 tx:2950 rx:0 RTS|DTR
        ...

Output with the attached patch:

        # cat /proc/tty/driver/serial
        serinfo:1.0 driver revision:
        0: uart:16450 mmio:0xF8031000 irq:65 tx:72 rx:0 RTS|DTR
        1: uart:16550A mmio:0xFF5E0000 irq:65 tx:2403 rx:74 RTS|DTR
        ...