Document the rationale for the armel build
Document the rationale for the armel build

Call the component xxx_arm5vte, because that's what it does. Explain
"armel", and more generally why this component exists, in a comment.

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