powerpc: Parse the command line before calling CAS

powerpc: Parse the command line before calling CAS

On POWER9 the hypervisor requires the guest to decide whether it would
like to use a hash or radix mmu model at the time it calls
ibm,client-architecture-support (CAS) based on what the hypervisor has
said it's allowed to do. It is possible to disable radix by passing
"disable_radix" on the command line. The next patch will add support for
the new CAS format, thus we need to parse the command line before calling
CAS so we can correctly select which mmu we would like to use.

Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Reviewed-by: Paul Mackerras <paulus@ozlabs.org>
Acked-by: Balbir Singh <bsingharora@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>