Add TPM crypto callback support for RSA key generation

[dgarske]

Required for https://github.com/wolfSSL/wolfPKCS11/pull/23

• Add TPM crypto callback support for RSA key generation
• Allow import of wolf ECC marked as private only (ECC_PRIVATEKEY_ONLY).
• Properly translate a TPM ECC signature verify error for compatibility.
• Fixes for building wolfCrypt without PEM to DER support.
• Improve the ECC key import scheme for signing.
• Improve logic for finding TPM curve in ECC key generation. A call to wc_ecc_make_key can use curve_id 0 (to detect), but we can get it from the "dp".
• Fix to make sure leading ECC sign leading zeros are removed when not required.
• Fix leading zero issue on verify.
• Fix for ECC encrypt secret integrity check failed due to zero pad issue.
• Fix for policy_sign issue when r or s is less than key size (needs zero padding).
• Support ECC KeyGen for signing or derive based on callback context eccKey or ecdhKey population.
• Cleanup KDF function return code checking to avoid scan-build warning.

[dgarske]

It should be documented that WOLFSSL_PUBLIC_MP is required for all the examples in examples/run_examples.sh to succeed. Any reason not to add it to the recommended wolfSSL config in the readme?

Also seeing a failure in the csr test:

:~/git/wolfTPM $ ./examples/csr/csr -cert
TPM2 CSR Example
Trying TPM @ /dev/spidev0.0 (33 MHz)
Trying TPM @ /dev/spidev0.1 (33 MHz)
Found TPM @ /dev/spidev0.1
TPM2: Caps 0x30000697, Did 0x001b, Vid 0x15d1, Rid 0x16
TPM2_Startup pass
TPM2_SelfTest pass
TPM2_ReadPublic Handle 0x81000200: pub 282, name 34, qualifiedName 34
Loading SRK: Storage 0x81000200 (282 bytes)
Reading 506 bytes from rsa_test_blob.raw
Public Area (size 278):
  Type: RSA (0x1), name: SHA256 (0xB), objAttr: 0x60460, authPolicy sz: 0
  RSA: sym algorithm: NULL (0x10), sym keyBits: 0, sym mode: Unknown (0x0)
       scheme: NULL (0x10), scheme hash: Unknown (0x0)
       keyBits: 2048, exponent: 0x10001, unique size 256
Reading the private part of the key
TPM2_Load Key Handle 0x80000001
Loaded key to 0x80000001
TPM2_FlushContext: Closed handle 0x80000001
Failure 0xffffff39: Random Number Generator failed

That is correct. The ECC encrypt scheme requires direct mp_ math functions. It has already been added to wolfSSL's --enable-wolftpm. See PR https://github.com/wolfSSL/wolfssl/pull/6683