x86/msr: Rename the WRMSRNS opcode macro to ASM_WRMSRNS (for KVM)

x86/msr: Rename the WRMSRNS opcode macro to ASM_WRMSRNS (for KVM)

Rename the WRMSRNS instruction opcode macro so that it doesn't collide
with X86_FEATURE_WRMSRNS when using token pasting to generate references
to X86_FEATURE_WRMSRNS.  KVM heavily uses token pasting to generate KVM's
set of support feature bits, and adding WRMSRNS support in KVM will run
will run afoul of the opcode macro.

  arch/x86/kvm/cpuid.c:719:37: error: pasting "X86_FEATURE_" and "" "" does not
                                      give a valid preprocessing token
  719 |         u32 __leaf = __feature_leaf(X86_FEATURE_##name);                \
      |                                     ^~~~~~~~~~~~

KVM has worked around one such collision in the past by #undef'ing the
problematic macro in order to avoid blocking a KVM rework, but such games
are generally undesirable, e.g. requires bleeding macro details into KVM,
risks weird behavior if what KVM is #undef'ing changes, etc.

Reviewed-by: Xin Li (Intel) <xin@zytor.com>
Link: https://lore.kernel.org/r/20250227010111.3222742-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>