m68k/coldfire: change pll var. to clk_pll

m68k/coldfire: change pll var. to clk_pll

DEFINE_CLK() makes the variable name be clk_xyz, so variable
'pll' should instead be 'clk_pll'.

In file included from ../arch/m68k/coldfire/m525x.c:12:
../arch/m68k/coldfire/m525x.c:29:30: error: 'pll' undeclared here (not in a function)
   29 |  CLKDEV_INIT(NULL, "pll.0", &pll),
      |                              ^~~
../include/linux/clkdev.h:30:10: note: in definition of macro 'CLKDEV_INIT'
   30 |   .clk = c, \
      |          ^
In file included from ../arch/m68k/coldfire/m525x.c:21:
../arch/m68k/include/asm/mcfclk.h:43:27: warning: 'clk_pll' defined but not used [-Wunused-variable]
   43 |         static struct clk clk_##clk_ref = { \
      |                           ^~~~
../arch/m68k/coldfire/m525x.c:25:1: note: in expansion of macro 'DEFINE_CLK'
   25 | DEFINE_CLK(pll, "pll.0", MCF_CLK);
      | ^~~~~~~~~~

Fixes: 63aadb77669a ("m68k: coldfire: use clkdev_lookup on most coldfire")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Greg Ungerer <gerg@linux-m68k.org>
Cc: linux-m68k@lists.linux-m68k.org
Cc: uclinux-dev@uclinux.org
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Ungerer <gerg@linux-m68k.org>