FAPI: Simplify key size retrieval
FAPI: Simplify key size retrieval

The EVP_PKEY_bits can be used to get the key size instead, which
simplifies the code. The function is available even in OpenSSL 1.0.2.

Signed-off-by: Petr Gotthard <8f56ce0e4bc573accd606cd7f5d0a5811375ffb0@centrum.cz>

tpm2-software/tpm2-tss,tpm2-software/tpm2-tss,01org/TPM2.0-TSS,01org/tpm2-tss,01org/tpm2-tss,01org/TPM2.0-TSS,01org/TPM2.0-TSS,01org/tpm2-tss,tpm2-software/tpm2-tss,01org/TPM2.0-TSS