By making the tqma6_iomuxc_spi() weak, this patch adds the possibility to
add a different function for this SPI configuration. This can be used
by other baseboards, that might have a different SPI setup.
This patch will be used by the upcoming WRU-IV board support which also
uses the TQMa6 SoM.
Signed-off-by: Stefan Roese <firstname.lastname@example.org>