mfd: avoid newly introduced compiler warning

Commit b158b69a ("mfd: rtsx: Simplify function return logic")
removed the use of the 'err' variable, but left the variable itself
around, resulting in gcc quite reasonably warning:

    drivers/mfd/rtsx_pcr.c: In function ‘rtsx_pci_set_pull_ctl’:
    drivers/mfd/rtsx_pcr.c:565:6: warning: unused variable ‘err’ [-Wunused-variable]
      int err;
          ^

Get rid of the unused variable, and avoid the new warning.

Cc: Javier Martinez Canillas <javier@osg.samsung.com>
Cc: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/mfd/rtsx_pcr.c

@@ -562,8 +562,6 @@ EXPORT_SYMBOL_GPL(rtsx_pci_write_ppbuf);
 
 static int rtsx_pci_set_pull_ctl(struct rtsx_pcr *pcr, const u32 *tbl)
 {
-	int err;
-
 	rtsx_pci_init_cmd(pcr);
 
 	while (*tbl & 0xFFFF0000) {