[PATCH] Correctly check read() return code

[ludovicrousseau]

read(2) returns a ssize_t (signed) and not a size_t (unsigned) or int

Fix the compiler warning:
os/linux_usbfs.c: In function ‘sysfs_get_active_config’:
os/linux_usbfs.c:366: warning: comparison of unsigned expression < 0 is always false

[segher]

Looks good. It might be better still to only check for -1
though (which, incidentally, would work with size_t as well).

[Ludovic Rousseau <rousseau@…>]

In [7802e4a3e38bcefccf96ae510ec2c6b7a959b8b5/libusb]:

Linux: Correctly catch read() errors for sysfs config descriptors

read(2) returns ssize_t (signed) and not size_t (unsigned) or int.

Silence "warning: comparison of unsigned expression < 0 is always false"
and fix #75.