libspdm_gen_x509_csr() wrap the code with crypto support algorithm

[rw8896]

https://github.com/DMTF/libspdm/blob/2756b67e0fcdee9abf8de109092255c83e9256ca/os_stub/cryptlib_mbedtls/pk/x509.c#L1981C1-L1981C40

Hi,

I wonder if we should rearrange the code and wrap it with corresponding crypto support options?

For example,
#if LIBSPDM_RSA_SSA_SUPPORT
case LIBSPDM_CRYPTO_NID_RSASSA2048:
case LIBSPDM_CRYPTO_NID_RSASSA3072:
case LIBSPDM_CRYPTO_NID_RSASSA4096:
#endif
#if LIBSPDM_RSA_PSS_SUPPORT
case LIBSPDM_CRYPTO_NID_RSAPSS2048:
case LIBSPDM_CRYPTO_NID_RSAPSS3072:
case LIBSPDM_CRYPTO_NID_RSAPSS4096:
#endif

Thanks!

[steven-bellock]

@rw8896 Sure. Feel free to submit a pull request.