staging: rtlwifi: halmac: halmac_api.c: Compress two lines into one line

Challenge suggested by coccinelle.
Compresses two lines into one line and remove unnecessary variable.

Signed-off-by: Payal Kshirsagar <payal.s.kshirsagar.98@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>