crypto: decouple curve25519 and idgen from random pool

This commit modularizes the curve25519 and idgen implementations in the
crypto subsystem.

Previously, curve25519.c and idgen.c were only compiled when
CONFIG_CRYPTO_RANDOM_POOL was enabled. However, cryptosoft.c (used by
software cipher support) has a direct dependency on curve25519 functions.
This caused linker errors (undefined reference to curve25519) when
software crypto was enabled but the random pool was disabled.

Changes:
- Introduce hidden Kconfig options CRYPTO_CURVE25519 and CRYPTO_IDGEN.
- Make CRYPTO_RANDOM_POOL select both CRYPTO_IDGEN and CRYPTO_CURVE25519.
- Make CRYPTO_CRYPTODEV_SOFTWARE_CRYPTO/KEYMGMT select CRYPTO_CURVE25519.
- Update CMakeLists.txt and Makefile to use the new config flags.

This ensures that required algorithms are automatically included in the
build regardless of whether the entropy pool is enabled.

Signed-off-by: karaketir16 <osmankaraketir@gmail.com>

crypto/Kconfig

@@ -43,11 +43,13 @@ config CRYPTO_CRYPTODEV
 config CRYPTO_CRYPTODEV_SOFTWARE_CRYPTO
 	bool "cryptodev software cipher support"
 	depends on CRYPTO_CRYPTODEV && CRYPTO_SW_AES
+	select CRYPTO_CURVE25519
 	default n
 
 config CRYPTO_CRYPTODEV_SOFTWARE_KEYMGMT
 	bool "cryptodev software key management support"
 	depends on CRYPTO_CRYPTODEV && !MTD_CONFIG_NONE
+	select CRYPTO_CURVE25519
 	default n
 
 if CRYPTO_CRYPTODEV_SOFTWARE_KEYMGMT
@@ -89,6 +91,8 @@ config CRYPTO_SW_AES
 
 config CRYPTO_RANDOM_POOL
 	bool "Entropy pool and strong random number generator"
+	select CRYPTO_IDGEN
+	select CRYPTO_CURVE25519
 	default n
 	---help---
 		Entropy pool gathers environmental noise from device drivers,
@@ -99,6 +103,14 @@ config CRYPTO_RANDOM_POOL
 		NOTE: May not actually be cyptographically secure, if
 		not enough entropy is made available to the entropy pool.
 
+config CRYPTO_CURVE25519
+	bool
+	default n
+
+config CRYPTO_IDGEN
+	bool
+	default n
+
 if CRYPTO_RANDOM_POOL
 
 config CRYPTO_RANDOM_POOL_COLLECT_IRQ_RANDOMNESS