powerpc: Add PowerPC Capabilities ELF note

Add the PowerPC name and the PPC_ELFNOTE_CAPABILITIES type in the
kernel binary ELF note. This type is a bitmap that can be used to
advertise kernel capabilities to userland.

This patch also defines PPCCAP_ULTRAVISOR_BIT as being the bit zero.

Suggested-by: Paul Mackerras <paulus@ozlabs.org>
Signed-off-by: Claudio Carvalho <cclaudio@linux.ibm.com>
[ maxiwell: Define the 'PowerPC' type in the elfnote.h ]
Signed-off-by: Maxiwell S. Garcia <maxiwell@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190829155021.2915-2-maxiwell@linux.ibm.com