x86/fpu: Standardize the parameter type of copy_kernel_to_fpregs()

Bring the __copy_fpstate_to_fpregs() and copy_fpstate_to_fpregs() functions
in line with the parameter passing convention of other kernel-to-FPU-registers
copying functions: pass around an in-memory FPU register state pointer,
instead of struct fpu *.

NOTE: This patch also changes the assembly constraint of the FXSAVE-leak
      workaround from 'fpu->fpregs_active' to 'fpstate' - but that is fine,
      as we only need a valid memory address there for the FILDL instruction.

Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Bobby Powers <bobbypowers@gmail.com>
Cc: Borislav Petkov <bp@alien8.de>
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: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/kvm/x86.c

@@ -7030,7 +7030,7 @@ void kvm_load_guest_fpu(struct kvm_vcpu *vcpu)
 	kvm_put_guest_xcr0(vcpu);
 	vcpu->guest_fpu_loaded = 1;
 	__kernel_fpu_begin();
-	__copy_kernel_to_fpregs(&vcpu->arch.guest_fpu);
+	__copy_kernel_to_fpregs(&vcpu->arch.guest_fpu.state);
 	trace_kvm_fpu(1);
 }