sh/PCI: Remove __init optimisations from IRQ mapping functions/data

Currently many IRQ mapping functions and data structures use the __init and
__initdata optimisations. These result in the relevant functions being
innaccessible after boot time.

However for deferred IRQ assignment it is important to have access to these
functions at PCI device enable time.

Therefore, remove the optimisation from the relevant data structures and
functions to prepare for deferred IRQ assignment.

Signed-off-by: Matthew Minter <matt@masarand.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: Rich Felker <dalias@libc.org>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>