virt: sev-guest: Replace dev_dbg() with pr_debug()

In preparation for moving code to arch/x86/coco/sev/core.c, replace
dev_dbg with pr_debug.

No functional change.

Signed-off-by: Nikunj A Dadhania <nikunj@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Reviewed-by: Borislav Petkov (AMD) <bp@alien8.de>
Tested-by: Peter Gonda <pgonda@google.com>
Link: https://lore.kernel.org/r/20240731150811.156771-2-nikunj@amd.com