lib/security: Fix broken if statements in gpg_validate_boot_files()

lib/security: Fix broken if statements in gpg_validate_boot_files()

The patch ccb478ac "Add encrypted file support" removes two
	result = KEXEC_LOAD_SIGNATURE_FAILURE;
statements from after the `if (verify_file_signature)` lines for the
kernel and cmdline signatures. This appears to have been a mistake that
snuck through testing, and would allow incorrect signatures to pass
validation.

Also fix up some confusing indenting in the decryption section.

Reported-by: Brett Grandbois <brett.grandbois@opengear.com>
Signed-off-by: Samuel Mendoza-Jonas <sam@mendozajonas.com>