brcmfmac: Fix station info rate information.

Txrate and rxrate in get_station got assigned first with value
in kbps and then divided by 100 to get it in 100kbps unit. The
problem with that is that type of rate is u16 which resulted
in incorrect values for high data rate values.

Reviewed-by: Arend Van Spriel <arend@broadcom.com>
Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Signed-off-by: Hante Meuleman <meuleman@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>