Cannot build for ARMCC on boards without TRNG

[c1728p9]

Since there is no entropy source some TLS functions are not present. These functions are never used directly, so GCC ignores them. ARMCC does not, and instead shows linker errors. Either directions to enable software only entropy need to be added, or the functions using the unavailable TLS functions need to be switched out.

CC: @SeppoTakalo @sg-

[SeppoTakalo]

Please open this bug on mbed OS repo.
If mbed OS cannot build on platforms without TRNG, then it is a mbed OS issue.

[c1728p9]

This should be fixed by ARMmbed/mbed-os#2915.