KVM: x86: Rename VEC_POS/REG_POS macro usages

KVM: x86: Rename VEC_POS/REG_POS macro usages

In preparation for moving most of the KVM's lapic helpers which
use VEC_POS/REG_POS macros to common APIC header for use in Secure
AVIC APIC driver, rename all VEC_POS/REG_POS macro usages to
APIC_VECTOR_TO_BIT_NUMBER/APIC_VECTOR_TO_REG_OFFSET and remove
VEC_POS/REG_POS.

While at it, clean up line wrap in find_highest_vector().

No functional change intended.

Signed-off-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>
Acked-by: Sean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/r/20250709033242.267892-5-Neeraj.Upadhyay@amd.com
Signed-off-by: Sean Christopherson <seanjc@google.com>