x86/hyperv: Set pv_info.name to "Hyper-V"

Michael reported that the x86/hyperv initialization code prints the
following dmesg when running in a VM on Hyper-V:

  [    0.000738] Booting paravirtualized kernel on bare hardware

Let the x86/hyperv initialization code set pv_info.name to "Hyper-V" so
dmesg reports correctly:

  [    0.000172] Booting paravirtualized kernel on Hyper-V

[ tglx: Folded build fix provided by Yue ]

Reported-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: Andrea Parri <parri.andrea@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Wei Liu <wei.liu@kernel.org>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Cc: YueHaibing <yuehaibing@huawei.com>
Link: https://lkml.kernel.org/r/20191015103502.13156-1-parri.andrea@gmail.com

arch/x86/kernel/cpu/mshyperv.c

@@ -216,6 +216,10 @@ static void __init ms_hyperv_init_platform(void)
 	int hv_host_info_ecx;
 	int hv_host_info_edx;
 
+#ifdef CONFIG_PARAVIRT
+	pv_info.name = "Hyper-V";
+#endif
+
 	/*
 	 * Extract the features and hints
 	 */