The patch making errno a positive value has another bug:
lseek was switched to return -errno instead of -1. This does not
work since we can lseek we can address the whole 4G address space,
have of which has a negative offset when interpreted as a signed
integer. Let lseek return -1 on failure again instead.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>