package/rng-tools: normalize github macro package name

This usage of <PKG>_NAME was introduced in commit f9e9c6349afe0
("package/rng-tools: bump to 6.7"). No other package uses <PKG>_NAME
this way.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

package/rng-tools/rng-tools.mk

@@ -5,7 +5,7 @@
 ################################################################################
 
 RNG_TOOLS_VERSION = 6.16
-RNG_TOOLS_SITE = $(call github,nhorman,$(RNG_TOOLS_NAME),v$(RNG_TOOLS_VERSION))
+RNG_TOOLS_SITE = $(call github,nhorman,rng-tools,v$(RNG_TOOLS_VERSION))
 RNG_TOOLS_LICENSE = GPL-2.0
 RNG_TOOLS_LICENSE_FILES = COPYING
 RNG_TOOLS_CPE_ID_VENDOR = rng-tools_project