[POWERPC] Support for "weird" MPICs and fixup mpc7448_hpc2

This adds a new hardware information table for mpic. This enables
the mpic code to deal with mpic controllers with different register
layouts and hardware behaviours.

This introduces CONFIG_MPIC_WEIRD.  For boards with non standard mpic
controllers, select CONFIG_MPIC_WEIRD and add its hardware information
in the mpic_infos[] array.

TSI108/109 PIC takes the first index of weird hardware information
table.  :)  The table can be extended. The Tsi108/109 PIC looks like
standard OpenPIC but, in fact, is different in register mapping and
behavior.

The patch does not affect the behavior of standard mpic.  If
CONFIG_MPIC_WEIRD is not defined, the code is essentially identical to
the current code.

[benh@kernel.crashing.org:
This patch is a slightly cleaned up version of Zang Roy's support for
the TSI108 MPIC variant. It also fixes up MPC7448_hpc2 to use the new
version of the type macros and changes the way MPIC is selected in
Kconfig to better match what is done for other system devices.
]

Signed-off-by: Roy Zang <tie-fei.zang@freescale.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>