soc: fsl: qe: drop use of IS_ERR_VALUE in qe_sdma_init()

Now that qe_muram_alloc() returns s32, adapt qe_sdma_init() and avoid
another few IS_ERR_VALUE() uses.

Reviewed-by: Timur Tabi <timur@kernel.org>
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Li Yang <leoyang.li@nxp.com>