NTB/msi: Fix ntbm_msi_request_threaded_irq() kernel-doc comment

Add the description of @msi_desc and change the @devname to @name
in ntbm_msi_request_threaded_irq() kernel-doc comment to remove
some warnings found by running scripts/kernel-doc, which is caused
by using 'make W=1'.
drivers/ntb/msi.c:285: warning: Function parameter or member 'name' not
described in 'ntbm_msi_request_threaded_irq'
drivers/ntb/msi.c:285: warning: Function parameter or member 'msi_desc'
not described in 'ntbm_msi_request_threaded_irq'
drivers/ntb/msi.c:285: warning: Excess function parameter 'devname'
description in 'ntbm_msi_request_threaded_irq'

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>