Revert "net: stmmac: use sysfs_streq() instead of strncmp()"

This reverts commit f72cd76b.
This patch is so broken, it hurts. Apparently no one reviewed it and it
passed the build testing (because the code was compiled out), but it was
obviously never compile-tested, since it produces the following build
error, due to an incomplete conversion where an extra argument was left,
although the function being called was left:

stmmac_main.c: In function ‘stmmac_cmdline_opt’:
stmmac_main.c:7586:28: error: too many arguments to function ‘sysfs_streq’
 7586 |                 } else if (sysfs_streq(opt, "pause:", 6)) {
      |                            ^~~~~~~~~~~
In file included from ../include/linux/bitmap.h:11,
                 from ../include/linux/cpumask.h:12,
                 from ../include/linux/smp.h:13,
                 from ../include/linux/lockdep.h:14,
                 from ../include/linux/mutex.h:17,
                 from ../include/linux/notifier.h:14,
                 from ../include/linux/clk.h:14,
                 from ../drivers/net/ethernet/stmicro/stmmac/stmmac_main.c:17:
../include/linux/string.h:185:13: note: declared here
  185 | extern bool sysfs_streq(const char *s1, const char *s2);
      |             ^~~~~~~~~~~

What's even worse is that the patch is flat out wrong. The stmmac_cmdline_opt()
function does not parse sysfs input, but cmdline input such as
"stmmaceth=tc:1,pause:1". The pattern of using strsep() followed by
strncmp() for such strings is not unique to stmmac, it can also be found
mainly in drivers under drivers/video/fbdev/.

With strncmp("tc:", 3), the code matches on the "tc:1" token properly.
With sysfs_streq("tc:"), it doesn't.

Fixes: f72cd76b

 ("net: stmmac: use sysfs_streq() instead of strncmp()")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Acked-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Link: https://lore.kernel.org/r/20221125105304.3012153-1-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>