i3c: ast2600: set variable ast2600_i3c_ops storage-class-specifier to static

i3c: ast2600: set variable ast2600_i3c_ops storage-class-specifier to static

smatch reports
drivers/i3c/master/ast2600-i3c-master.c:121:34: warning: symbol
  'ast2600_i3c_ops' was not declared. Should it be static?

This variable is only used in its defining file, so it should be static.

Signed-off-by: Tom Rix <trix@redhat.com>
Reviewed-by: Jeremy Kerr <jk@codeconstruct.com.au>
Link: https://lore.kernel.org/r/20230429134601.2688558-1-trix@redhat.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>