This update for ovmf fixes the following issues:

- Update firmware descriptors to remove tab whitespace (bsc#1247847)
    * Replace tab whitespace with spaces in 50-ovmf-x86_64-sev.json
    * Replace tab whitespace with spaces in 50-ovmf-x86_64-sev-snp.json 
- Update firmware descriptors for SEV-SNP (bsc#1247847)
    * Add 50-ovmf-x86_64-sev-snp.json to support the 'amd-sev-snp' feature.
    * Remove the sev-snp feature from 50-ovmf-x86_64-sev.json.