readme: Addressed review comments
readme: Addressed review comments

Signed-off-by: Minos Galanakis <bb9c15d46ed7ecad5455c4c22ac024636068eda6@arm.com>

ARMmbed/mbedtls,Mbed-TLS/mbedtls,NXPmicro/mbedtls,NXPmicro/mbedtls,ARMmbed/mbedtls,ARMmbed/mbedtls,Mbed-TLS/mbedtls,Mbed-TLS/mbedtls,NXPmicro/mbedtls,Mbed-TLS/mbedtls,ARMmbed/mbedtls,NXPmicro/mbedtls