soc: fsl: dpio: avoid stack usage warning

A 1024 byte variable on the stack will warn on any 32-bit architecture
during compile-testing, and is generally a bad idea anyway:

fsl/dpio/dpio-service.c: In function 'dpaa2_io_service_enqueue_multiple_desc_fq':
fsl/dpio/dpio-service.c:495:1: error: the frame size of 1032 bytes is larger than 1024 bytes [-Werror=frame-larger-than=]

There are currently no callers of this function, so I cannot tell whether
dynamic memory allocation is allowed once callers are added. Change
it to kcalloc for now, if anyone gets a warning about calling this in
atomic context after they start using it, they can fix it later.

Link: https://lore.kernel.org/r/20200408185834.434784-1-arnd@arndb.de
Fixes: 9d988097

 ("soc: fsl: dpio: Adding QMAN multiple enqueue interface")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>