mm: cma: remove unnecessary initialization of ret

The ret variable can be defined without assigning a value, as it is
assigned before use.

Link: https://lkml.kernel.org/r/20231205021751.100459-1-zeming@nfschina.comSigned-off-by: Li zeming <zeming@nfschina.com>
Reviewed-by: Andrew Morton <akpm@linux-foudation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/cma.c

@@ -244,7 +244,7 @@ int __init cma_declare_contiguous_nid(phys_addr_t base,
 {
 	phys_addr_t memblock_end = memblock_end_of_DRAM();
 	phys_addr_t highmem_start;
-	int ret = 0;
+	int ret;
 
 	/*
 	 * We can't use __pa(high_memory) directly, since high_memory