MIPS: Add & use CP0_EntryHi ASID definitions

Add definitions for the ASID field in CP0_EntryHi (along with the soon
to be used ASIDX field), and use them in a few previously hardcoded
cases.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Manuel Lauss <manuel.lauss@gmail.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/13205/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/arch/mips/pci/pci-alchemy.c b/arch/mips/pci/pci-alchemy.c
index 2895263..c8994c1 100644
--- a/arch/mips/pci/pci-alchemy.c
+++ b/arch/mips/pci/pci-alchemy.c
@@ -76,7 +76,7 @@
 	unsigned long old_ctx;
 
 	/* Save old context and create impossible VPN2 value */
-	old_ctx = read_c0_entryhi() & 0xff;
+	old_ctx = read_c0_entryhi() & MIPS_ENTRYHI_ASID;
 	old_pagemask = read_c0_pagemask();
 	write_c0_index(entry);
 	write_c0_pagemask(pagemask);