busybox: Provide /bin/ash when usrmerge is enabled

When usrmerge is enabled, scripts that were explicitly using #!/bin/ash will cause a QA Error like the following:

QA Issue: bar.sh contained in package foo requires /bin/ash, but no providers found in RDEPENDS_foo? [file-rdeps].

It seems perfectly acceptable for scripts to use /bin/ash so provide it along with /bin/sh.

---
 meta/recipes-core/busybox/busybox.inc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index 10582a7534..c07162f6b4 100644
@@ -454,4 +454,4 @@ pkg_prerm_${PN}-syslog () {
 	fi
 }
 
-RPROVIDES_${PN} += "${@bb.utils.contains('DISTRO_FEATURES', 'usrmerge', '/bin/sh', '', d)}"
+RPROVIDES_${PN} += "${@bb.utils.contains('DISTRO_FEATURES', 'usrmerge', '/bin/sh /bin/ash', '', d)}"

2.14.5