[XEN][POWERPC] go ultra conservative on CI IO routines

[XEN][POWERPC] go ultra conservative on CI IO routines
The following patch contains:
 - Code that uses SLBIE for ERAT flush rather than TLBIE.  Erratum #16
   says to use SLBIE bit a TLBIE should do it and is "less
   distruptive".
 - Machine Check issues
   - Track CI mode while cache is still enabled
   - Use r7 to indicate that the IO is still pending while CI is on
 - The right sync for the right reasons
Signed-off-by: Jimi Xenidis <jimix@watson.ibm.com>
Signed-off-by: Hollis Blanchard <hollisb@us.ibm.com>
--HG--
extra : transplant_source : %27m9%82%2A%21%DA%13%DD%DD%8B%C4%091a%05%D2%FA88