Cargo.toml: Specify rdrand as dependency

Without the "dep:_" prefix, packagers can mistake this for being a
feature, rather than the enablement of an optional dependency.

Signed-off-by: Tyler Fanelli <[email protected]>

Cargo.toml

@@ -38,7 +38,7 @@ doc = false
 
 [features]
 default = ["sev", "snp"]
-openssl = ["dep:openssl", "rdrand"]
+openssl = ["dep:openssl", "dep:rdrand"]
 hw_tests = []
 dangerous_hw_tests = ["hw_tests"]
 sev = []