KVM: MAINTAINERS improvements

Remove nonexistent files, allow less awkward expressions when
extracting arch-specific information, and only return relevant
information when using arch-specific expressions. Additionally
add include/trace/events/kvm.h, arch/*/include/uapi/asm/kvm*,
and arch/powerpc/kernel/kvm* to appropriate sections. The arch-
specific expressions are now:

 /KVM/                                        -- All KVM
 /\(KVM\)|\(KVM\/x86\)/                       -- X86
 /\(KVM\)|\(KVM\/x86\)|\(KVM\/amd\)/          -- X86 plus AMD
 /\(KVM\)|\(KVM\/arm\)/                       -- ARM
 /\(KVM\)|\(KVM\/arm\)|\(KVM\/arm64\)/        -- ARM plus ARM64
 /\(KVM\)|\(KVM\/powerpc\)/                   -- POWERPC
 /\(KVM\)|\(KVM\/s390\)/                      -- S390
 /\(KVM\)|\(KVM\/mips\)/                      -- MIPS

Signed-off-by: Andrew Jones <drjones@redhat.com>
Acked-by: Cornelia Huck <cohuck@redhat.com>
Acked-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>