nrf_security: Increase default maximum size of MPI

Max MPI size is set to 256 by default. This needs to be increased
to 384 to handle RSA-3072 signature.

Signed-off-by: Ravi Dondaputi <[email protected]>

Author: rado17

subsys/nrf_security/Kconfig.legacy

@@ -288,6 +288,7 @@ config MBEDTLS_MPI_MAX_SIZE
 	prompt "Maximum number of bytes for usable MPIs." if !(CC312_BACKEND || CC310_BACKEND)
 	default 256 if CC310_BACKEND
 	default 384 if CC312_BACKEND
+	default 384 # Needed to support RSA 3072
 	range 256 2048
 
 config MBEDTLS_LEGACY_CRYPTO_C_SILENCE_DEPRECATION