libfdt: avoid shadowing "err" in FDT_RW_CHECK_HEADER

FDT_RW_CHECK_HEADER declares an internal variable named "err" which is
far too generic and will produce the following -Wshadow warnings:

libfdt/fdt_rw.c: In function 'fdt_add_mem_rsv':
libfdt/fdt_rw.c:177:2: error: declaration of 'err' shadows a previous
local [-Werror=shadow]
libfdt/fdt_rw.c:175:6: error: shadowed declaration is here
[-Werror=shadow]
libfdt/fdt_rw.c: In function 'fdt_del_mem_rsv':
libfdt/fdt_rw.c:194:2: error: declaration of 'err' shadows a previous
local [-Werror=shadow]
libfdt/fdt_rw.c:192:6: error: shadowed declaration is here
[-Werror=shadow]
libfdt/fdt_rw.c: In function 'fdt_set_name':
...

Since this variable is only used internally in the macro, rename to
__err which should be prefixed enough not to cause new shadow warnings.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>

libfdt/fdt_rw.c

@@ -84,9 +84,9 @@ static int _fdt_rw_check_header(void *fdt)
 
 #define FDT_RW_CHECK_HEADER(fdt) \
 	{ \
-		int err; \
-		if ((err = _fdt_rw_check_header(fdt)) != 0) \
-			return err; \
+		int __err; \
+		if ((__err = _fdt_rw_check_header(fdt)) != 0) \
+			return __err; \
 	}
 
 static inline int _fdt_data_size(void *fdt)