crypto/ccp: Skip SNP_INIT if preparation fails

crypto/ccp: Skip SNP_INIT if preparation fails

If snp_prepare() fails, SNP_INIT will fail, so skip it and return early.

Note that this is not a change in initialization behavior: if SNP_INIT fails
even before this change, it will still return an error and
__sev_snp_init_locked() will fail initialization of other SEV modes.

Signed-off-by: Tycho Andersen (AMD) <tycho@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Nikunj A Dadhania <nikunj@amd.com>
Link: https://lore.kernel.org/20260429155636.540040-1-tycho@kernel.org