fsl-dspi: Correctly configure 'CTAR' register

commit 1d815532095655806dbb2aba8f2f99422b94b7a5 from
https://source.codeaurora.org/external/autobsps32/linux



Issue: ALB-4840
Signed-off-by: Ciprian Marian Costea <ciprianmarian.costea@nxp.com>
Signed-off-by: Xulin Sun <xulin.sun@windriver.com>