dma: imx-dma: fix signedness bug
dma: imx-dma: fix signedness bug

mxdmac->channel was unsigned, so check (imxdmac->channel < 0) for
failed imx_dma_request_by_prio() made no sence.  Explicitly check
signed values.
Also, fix uninitialzed use of ret.

Signed-off-by: Vasiliy Kulikov <bf62e7c380ff4449c5c3c5c39150b7660ee28ecb@gmail.com>
Signed-off-by: Sascha Hauer <c00cbc2b736c26791a3822db86f8796fe9efff67@pengutronix.de>
Signed-off-by: Dan Williams <24ee2bf0bd8ac766c348bf1f0639943bac1535c6@intel.com>

TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs