[gen3] disable some of the elliptic-curves not in use to save flash space

[avtolstoy]

Problem

nRF52840 CC310 hardware crypto support for each particular elliptic curve takes about 700 bytes in closed source Nordic CC310 support library (see ssi_ecpki_domain_* symbols in the map file).

Solution

Stub out ECC curves not supported by mbedTLS!

Original sizes

   text	   data	    bss	    dec	    hex	filename
 481540	   2588	  60404	 544532	  84f14	../../../build/target/system-part1/platform-12-m/system-part1.elf
   text	   data	    bss	    dec	    hex	filename
 511904	   2660	  61552	 576116	  8ca74	../../../build/target/system-part1/platform-13-m/system-part1.elf
   text	   data	    bss	    dec	    hex	filename
 512224	   2692	  61560	 576476	  8cbdc	../../../build/target/system-part1/platform-23-m/system-part1.elf
   text	   data	    bss	    dec	    hex	filename
 508688	   2692	  61560	 572940	  8be0c	../../../build/target/system-part1/platform-25-m/system-part1.elf
   text	   data	    bss	    dec	    hex	filename
 543608	   3076	  62592	 609276	  94bfc	../../../build/target/system-part1/platform-26-m/system-part1.elf

After PR

   text	   data	    bss	    dec	    hex	filename
 474180	   2588	  60408	 537176	  83258	../../../build/target/system-part1/platform-12-m/system-part1.elf
   text	   data	    bss	    dec	    hex	filename
 504528	   2660	  61556	 568744	  8ada8	../../../build/target/system-part1/platform-13-m/system-part1.elf
   text	   data	    bss	    dec	    hex	filename
 504864	   2692	  61564	 569120	  8af20	../../../build/target/system-part1/platform-23-m/system-part1.elf
   text	   data	    bss	    dec	    hex	filename
 501328	   2692	  61564	 565584	  8a150	../../../build/target/system-part1/platform-25-m/system-part1.elf
   text	   data	    bss	    dec	    hex	filename
 536248	   3068	  62596	 601912	  92f38	../../../build/target/system-part1/platform-26-m/system-part1.elf

About 8K savings!

Steps to Test

N/A

Example App

N/A

References

N/A

---

Completeness

• User is totes amazing for contributing!
• Contributor has signed CLA (Info here)
• Problem and Solution clearly stated
• Run unit/integration/application tests on device
• Added documentation
• Added to CHANGELOG.md after merging (add links to docs and issues)

[sergeuz]

Niiiice