powerpc: Remove CPU_FTR_HVMODE from CPU_FTRS_ALWAYS

We potentially clear CPU_FTR_HVMODE at runtime in __init_hvmode_206(),
so we must make sure it's not set in CPU_FTRS_ALWAYS.

This doesn't hurt us in practice at the moment, because we don't support
compiling only for CPUs that support CPU_FTR_HVMODE.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>