iwlwifi: fix firmware names for 9000 and A000 series hw

iwlwifi 9000 and a0000 series hw contains an extra dash in firmware
file name as seeen in modinfo output for kernel 4.14:

firmware:       iwlwifi-9260-th-b0-jf-b0--34.ucode
firmware:       iwlwifi-9260-th-a0-jf-a0--34.ucode
firmware:       iwlwifi-9000-pu-a0-jf-b0--34.ucode
firmware:       iwlwifi-9000-pu-a0-jf-a0--34.ucode
firmware:       iwlwifi-QuQnj-a0-hr-a0--34.ucode
firmware:       iwlwifi-QuQnj-a0-jf-b0--34.ucode
firmware:       iwlwifi-QuQnj-f0-hr-a0--34.ucode
firmware:       iwlwifi-Qu-a0-jf-b0--34.ucode
firmware:       iwlwifi-Qu-a0-hr-a0--34.ucode

Fix that by dropping the extra adding of '"-"'.

Signed-off-by: Thomas Backlund <tmb@mageia.org>
Cc: stable@vger.kernel.org # 4.13
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>