staging: vt6656: Fix calling conditions of vnt_set_bss_mode

vnt_set_bss_mode needs to be called on all changes to BSS_CHANGED_BASIC_RATES,
BSS_CHANGED_ERP_PREAMBLE and BSS_CHANGED_ERP_SLOT

Remove all other calls and vnt_update_ifs which is called in vnt_set_bss_mode.

Fixes an issue that preamble mode is not being updated correctly.

Fixes: c1260357

 ("staging: vt6656: Only call vnt_set_bss_mode on basic rates change.")
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Malcolm Priestley <tvboxspy@gmail.com>
Link: https://lore.kernel.org/r/44110801-6234-50d8-c583-9388f04b486c@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>