x86/paravirt: split paravirt definitions into paravirt_types.h

Split the monolithic asm/paravirt.h into separate paravirt.h (inlines and other
"active" definitions), and paravirt_types.h (types, constants and other "passive"
definitions).  This makes it easier to use the type/constant definitions without
pulling in everything else and causing circular dependency problems.

[ Impact: cleanup ]

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>