extmod/mbedtls: Enable elliptic curve DH and DSA cryptography.

This is necessary to access sites that only support these protocols.

The rp2 port already has ECDH enabled, so this just adds ECDSA there.  The
other ports now gain both ECDH and ECDSA.  The code size increase is:

- rp2 (PICO_W): +2916 bytes flash, +24 bytes BSS
- stm32 (PYBD_SF6): +20480 bytes flash, +32 bytes data, +48 bytes BSS
- mimxrt (TEENSY41): +20708 bytes flash, +32 bytes data, +48 bytes BSS
- unix (standard x86-64): +39344 executable, +1744 bytes data, +96 BSS

This is obviously a large increase in code size.  But there doesn't seem to
be any other option because without elliptic curve cryptography devices are
partially cut off from the internet.  For use cases that require small
firmware size, they'll need to build custom firmware with a custom mbedtls
config.

Signed-off-by: Damien George <damien@micropython.org>

ports/mimxrt/mbedtls/mbedtls_config.h

@@ -26,9 +26,6 @@
 #ifndef MICROPY_INCLUDED_MBEDTLS_CONFIG_H
 #define MICROPY_INCLUDED_MBEDTLS_CONFIG_H
 
-// Enable mbedtls modules
-// #define MBEDTLS_ECP_C
-
 // Set MicroPython-specific options.
 #define MICROPY_MBEDTLS_CONFIG_BARE_METAL (1)