hwrng: drivers - add missing Arm & Cavium MODULE_DESCRIPTION() macros

With ARCH=arm64, make allmodconfig && make W=1 C=1 reports:
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/char/hw_random/cavium-rng.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/char/hw_random/cavium-rng-vf.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/char/hw_random/arm_smccc_trng.o

Add the missing invocations of the MODULE_DESCRIPTION() macro.
Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/char/hw_random/arm_smccc_trng.c

@@ -118,4 +118,5 @@ module_platform_driver(smccc_trng_driver);
 
 MODULE_ALIAS("platform:smccc_trng");
 MODULE_AUTHOR("Andre Przywara");
+MODULE_DESCRIPTION("Arm SMCCC TRNG firmware interface support");
 MODULE_LICENSE("GPL");

drivers/char/hw_random/cavium-rng-vf.c

@@ -266,4 +266,5 @@ static struct pci_driver cavium_rng_vf_driver = {
 module_pci_driver(cavium_rng_vf_driver);
 
 MODULE_AUTHOR("Omer Khaliq <okhaliq@caviumnetworks.com>");
+MODULE_DESCRIPTION("Cavium ThunderX Random Number Generator VF support");
 MODULE_LICENSE("GPL v2");

drivers/char/hw_random/cavium-rng.c

@@ -88,4 +88,5 @@ static struct pci_driver cavium_rng_pf_driver = {
 
 module_pci_driver(cavium_rng_pf_driver);
 MODULE_AUTHOR("Omer Khaliq <okhaliq@caviumnetworks.com>");
+MODULE_DESCRIPTION("Cavium ThunderX Random Number Generator support");
 MODULE_LICENSE("GPL v2");