Documentation: virt: Fix up pre-formatted text block for SEV ioctls

A missing newline after "::" resulted in the htmldocs build failing to
recognize the start of a pre-formatted block of text, resulting in

  kernel/linux/Documentation/virt/coco/sev-guest.rst:75: WARNING: Inline emphasis start-string without end-string.
  kernel/linux/Documentation/virt/coco/sev-guest.rst:78: WARNING: Inline emphasis start-string without end-string.
  kernel/linux/Documentation/virt/coco/sev-guest.rst:81: WARNING: Inline emphasis start-string without end-string.
  kernel/linux/Documentation/virt/coco/sev-guest.rst:83: WARNING: Definition list ends without a blank line; unexpected unindent.

Fix it.

Fixes: f5db8841 ("crypto: ccp: Add the SNP_PLATFORM_STATUS command")
Closes: https://lore.kernel.org/linux-next/20240202145932.31c62fd6@canb.auug.org.au/Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20240202160544.2297320-1-michael.roth@amd.com

Documentation/virt/coco/sev-guest.rst

@@ -71,6 +71,7 @@ The host ioctls are issued to a file descriptor of the /dev/sev device.
 The ioctl accepts the command ID/input structure documented below.
 
 ::
+
         struct sev_issue_cmd {
                 /* Command ID */
                 __u32 cmd;