x86/fpu: Rename fpu_alloc() to fpstate_alloc()

Use the fpu__*() namespace for fpstate_alloc() as well.

Also add a comment about FPU state alignment.

Reviewed-by: Borislav Petkov <bp@alien8.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/kvm/x86.c

@@ -7007,7 +7007,7 @@ int fx_init(struct kvm_vcpu *vcpu)
 {
 	int err;
 
-	err = fpu_alloc(&vcpu->arch.guest_fpu);
+	err = fpstate_alloc(&vcpu->arch.guest_fpu);
 	if (err)
 		return err;