From: YueHaibing <redacted>
Date: Sat, 29 Dec 2018 14:45:23 +0800

gcc warn this:
net/ipv4/fib_rules.c:203 fib_empty_table() warn:
 always true condition '(id <= 4294967295) => (0-u32max <= u32max)'

'id' is u32, which always not greater than RT_TABLE_MAX
(0xFFFFFFFF), So add a check to break while wrap around.

Signed-off-by: YueHaibing <redacted>
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v2: clean up exit conditions

Applied.