adjust include paths

[GregSlazinski]

replace
https://github.com/ARMmbed/mbedtls/blob/development/include/mbedtls/ssl.h#L55
https://github.com/ARMmbed/mbedtls/blob/development/include/mbedtls/platform.h#L33
#include "mbedtls/platform_time.h"
with
#include "platform_time.h"

these files are in the same folder, so the paths should not include "mbedtls/"

I'm trying to include the headers in a standalone project and I'm getting errors about"mbedtls/*" file not found.
After doing the replacements, the headers compile OK.

[RonEld]

Hi @GregSlazinski Thank you for raising this issue!
I believe that this is a duplicate of #857 , and that #921 fixes this issue