memory leak in mbedtls_x509_csr_parse

[RonEld]

Note: This is just a template, so feel free to use/remove the unnecessary things

Description

• Type: Bug
• Priority: Major
  Raised by @catenacyber through mail.
  Memory leak in mbedtls_x509_csr_parse(): in case mbedtls_x509_csr_parse_der() fails, pem is not freed.
  This issue is to track PR Fix memory leak in mbedtls_x509_csr_parse #1621

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Bug

OS
Mbed linux

mbed TLS build:
Version: development branch
OS version: x.x.x
Configuration: please attach config.h file where possible
Compiler and options (if you used a pre-built binary, please indicate how you obtained it):
Additional environment information:
Discovered by oss fuzzer tool

[ciarmcom]

ARM Internal Ref: IOTSSL-2287

[simonbutcher]

PR's to address this problem - development #1621, mbedtls-2.7 #1772, mbedtls-2.1 #1774 - have now been merged. This issue can now be closed.