staging: wfx: load the firmware faster

staging: wfx: load the firmware faster

During the loading of the firmware, the WFX_DCA_GET register provide the
number available bytes in the receiving buffer. It is not necessary to
access to the WFX_DCA_GET after sent of each firmware fragment.

This patch allows to send the firmware:
  - in 64ms instead of 130ms using SDIO bus
  - in 78ms instead of 115ms using SPI bus

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20200701150707.222985-6-Jerome.Pouiller@silabs.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>