KVM: SVM: Replace hard-coded value 0x1FF with the corresponding macro

KVM: SVM: Replace hard-coded value 0x1FF with the corresponding macro

The lower 9-bit field in EXITINFO2 represents an index into the AVIC
Physical/Logical APIC ID table for a AVIC_INCOMPLETE_IPI #VMEXIT. Since
the index into the Logical APIC ID table is just 8 bits, this field is
actually bound by the bit-width of the index into the AVIC Physical ID
table which is represented by AVIC_PHYSICAL_MAX_INDEX_MASK. So, use that
macro to mask EXITINFO2.Index instead of hard coding 0x1FF in
avic_incomplete_ipi_interception().

Co-developed-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Signed-off-by: Naveen N Rao (AMD) <naveen@kernel.org>
Link: https://lore.kernel.org/r/95795f449c68bffcb3e1789ee2b0b7393711d37d.1757009416.git.naveen@kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>