PCI: use weak functions for MSI arch-specific functions

PCI: use weak functions for MSI arch-specific functions

Until now, the MSI architecture-specific functions could be overloaded
using a fairly complex set of #define and compile-time
conditionals. In order to prepare for the introduction of the msi_chip
infrastructure, it is desirable to switch all those functions to use
the 'weak' mechanism. This commit converts all the architectures that
were overidding those MSI functions to use the new strategy.

Note that we keep two separate, non-weak, functions
default_teardown_msi_irqs() and default_restore_msi_irqs() for the
default behavior of the arch_teardown_msi_irqs() and
arch_restore_msi_irqs(), as the default behavior is needed by x86 PCI
code.

Signed-off-by: Thomas Petazzoni <[email protected]>
Acked-by: Bjorn Helgaas <[email protected]>
Acked-by: Benjamin Herrenschmidt <[email protected]>
Tested-by: Daniel Price <[email protected]>
Tested-by: Thierry Reding <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: [email protected]
Cc: Martin Schwidefsky <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: [email protected]
Cc: Russell King <[email protected]>
Cc: Tony Luck <[email protected]>
Cc: Fenghua Yu <[email protected]>
Cc: [email protected]
Cc: Ralf Baechle <[email protected]>
Cc: [email protected]
Cc: David S. Miller <[email protected]>
Cc: [email protected]
Cc: Chris Metcalf <[email protected]>
Signed-off-by: Jason Cooper <[email protected]>