MIPS: Malta: Remove ttyS2 serial for CMP platforms

Commit 225ae5fd
"MIPS: Malta: Fix interupt number of CBUS UART"

fixed the IRQ number for the ttyS2 CBUS UART. However, this now
conflicts with the GIC IPI1 interrupt in CMP platforms. The Malta
interrupt code arbitrarily binds IPIs to INT2 and INT3 and since
ttyS2 uses the INT2 IRQ line, closing the device disables the
INT2 interrupt and this effectively disables the IPI1 interrupt
as well. This patch is mainly a workaround until the Malta code
is fixed properly.

Signed-off-by: Leonid Yegoshin <Leonid.Yegoshin@imgtec.com>
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Signed-off-by: John Crispin <blogic@openwrt.org>
Patchwork: http://patchwork.linux-mips.org/patch/6045/