watchdog: sp805: Use devm_clk_get_optional()

Replace open coded variants of devm_clk_get_optional().

While at it, drop unneeded OF and ACPI dependency as the APIs in use
are provider agnostic.

Cc: Srinath Mannam <srinath.mannam@broadcom.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Srinath Mannam <srinath.mannam@broadcom.com>
Link: https://lore.kernel.org/r/20210517174456.22050-1-andriy.shevchenko@linux.intel.com


Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>