stress-ng: Add bash to RDEPENDS_stress-ng-bash-completion

stress-ng: Add bash to RDEPENDS_stress-ng-bash-completion

Fixed:
$ bitbake stress-ng bash -ccleansstate && bitbake stress-ng
ERROR: stress-ng-0.10.00-r0 do_package_qa: QA Issue: /usr/share/bash-completion/completions/stress-ng contained in package stress-ng-bash-completion requires /bin/bash, but no providers found in RDEPENDS_stress-ng-bash-completion? [file-rdeps]

Signed-off-by: Robert Yang <liezhi.yang@windriver.com>