SPI: mxc_spi: remove second reset from ECSPI config handler

the second reset prevents other registers to be written.
This will prevent to have the correct signal levels for
SCLK before writing to the config reg in spi_xchg_single.

Tested with GPIO based chipselect and SPI_MODE_3 on i.MX6S

Signed-off-by: Markus Niebel <Markus.Niebel@tq-group.com>
Acked-by: Stefano Babic <sbabic@denx.de>
Reviewed-by: Jagannadha Sutradharudu Teki <jagannadh.teki@gmail.com>