powerpc/44x: Fix PCI MSI support for Maui APM821xx SoC and Bluestone board

This patch consists of:
- Enable PCI MSI as default for Bluestone board
- Change definition of number of MSI interrupts as it depends on SoC
- Fix returning ENODEV as finding MSI node
- Fix MSI physical high and low address
- Keep MSI data logically

Signed-off-by: Mai La <mla@apm.com>
Signed-off-by: Josh Boyer <jwboyer@gmail.com>