hw/nvme: Add NVMe NGUID property

hw/nvme: Add NVMe NGUID property

This patch adds a way to specify an NGUID for a given NVMe Namespace using a
string of hexadecimal digits with an optional '-' separator to group bytes. For
instance:

-device nvme-ns,nguid="e9accd3b83904e13167cf0593437f57d"

If provided, the NGUID will be part of the Namespace Identification Descriptor
list and the Identify Namespace data.

Signed-off-by: Roque Arcudia Hernandez <roqueh@google.com>
Signed-off-by: Nabih Estefan <nabihestefan@google.com>
Reviewed-by: Klaus Jensen <k.jensen@samsung.com>
Signed-off-by: Klaus Jensen <k.jensen@samsung.com>