net/wan/fsl_ucc_hdlc: avoid use of IS_ERR_VALUE()

When building this on a 64-bit platform gcc rightly warns that the
error checking is broken (-ENOMEM stored in an u32 does not compare
greater than (unsigned long)-MAX_ERRNO). Instead, now that
qe_muram_alloc() returns s32, use that type to store the return value
and use standard kernel style "ret < 0".

Reviewed-by: Timur Tabi <timur@kernel.org>
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Li Yang <leoyang.li@nxp.com>