bus: fsl-mc-msi: Fix a little doc-rot pertaining to 'np' to 'fwnode' conversion

bus: fsl-mc-msi: Fix a little doc-rot pertaining to 'np' to 'fwnode' conversion

Fixes the following W=1 kernel build warning(s):

 drivers/bus/fsl-mc/fsl-mc-msi.c:164: warning: Function parameter or member 'fwnode' not described in 'fsl_mc_msi_create_irq_domain'
 drivers/bus/fsl-mc/fsl-mc-msi.c:164: warning: Excess function parameter 'np' description in 'fsl_mc_msi_create_irq_domain'

Cc: Stuart Yoder <stuyoder@gmail.com>
Cc: German Rivera <German.Rivera@freescale.com>
Reviewed-by: Laurentiu Tudor <laurentiu.tudor@nxp.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20210617110500.15907-7-lee.jones@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>