i965: Validate textures before altering driver state

i965: Validate textures before altering driver state

Validation may kick off copies and subsequently color resolves.
Color resolves (and the copies themselves if ending up in meta path)
will overwrite the internal driver state but are not prepared to
restore it. Instead of adding that capability the validation can be
simply performed before the state is updated.

Signed-off-by: Topi Pohjolainen <topi.pohjolainen@intel.com>