rsa : Compile Modular Exponentiation files based on CONFIG_RSA_SOFTWARE_EXP

Remove dependency of rsa_mod_exp from CONFIG_FIT_SIGNATURE.
As rsa modular exponentiation is an independent module
and can be invoked independently.

Signed-off-by: Gaurav Rana <gaurav.rana@freescale.com>
Acked-by: Simon Glass <sjg@chromium.org>
Reviewed-by: York Sun <yorksun@freescale.com>

drivers/crypto/rsa_mod_exp/Makefile

@@ -4,4 +4,5 @@
 # SPDX-License-Identifier:	GPL-2.0+
 #
 
-obj-$(CONFIG_RSA) += mod_exp_uclass.o mod_exp_sw.o
+obj-$(CONFIG_RSA) += mod_exp_uclass.o
+obj-$(CONFIG_RSA_SOFTWARE_EXP) += mod_exp_sw.o

lib/rsa/Makefile

@@ -7,4 +7,5 @@
 # SPDX-License-Identifier:	GPL-2.0+
 #
 
-obj-$(CONFIG_FIT_SIGNATURE) += rsa-verify.o rsa-checksum.o rsa-mod-exp.o
+obj-$(CONFIG_FIT_SIGNATURE) += rsa-verify.o rsa-checksum.o
+obj-$(CONFIG_RSA_SOFTWARE_EXP) += rsa-mod-exp.o