deepin: riscv: config: auto generate module sign key

deepin inclusion
category: bugfix

CONFIG_MODULE_SIG_KEY="" is not a vaild config will make
"make bindeb-pkg -j$(nproc)" failed in sign module pass.
Fix by removing the config setting to use the default value
"certs/signing_key.pem" which will be auto generated.

Signed-off-by: Wentao Guan <guanwentao@uniontech.com>

Author: opsiff

arch/riscv/configs/deepin_riscv64_desktop_defconfig

@@ -2768,7 +2768,6 @@ CONFIG_CRYPTO_GHASH_RISCV64=m
 CONFIG_CRYPTO_DEV_CHELSIO=m
 CONFIG_CRYPTO_DEV_VIRTIO=m
 CONFIG_PKCS8_PRIVATE_KEY_PARSER=m
-CONFIG_MODULE_SIG_KEY=""
 CONFIG_SECONDARY_TRUSTED_KEYRING=y
 CONFIG_SYSTEM_BLACKLIST_KEYRING=y
 # CONFIG_XZ_DEC_X86 is not set