drivers/pwm: Remove __init initializer for pwm_add_table

drivers/pwm: Remove __init initializer for pwm_add_table

For platforms where there are DT, some early MFD modules can reguster
lookup tables. Remove __init initializer so that this works. This is
similar to gpio_add_lookup_table which allows later initializations

CC: Samuel Ortiz <sameo@linux.intel.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Alexandre Courbot <gnurou@gmail.com>
Cc: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Shobhit Kumar <shobhit.kumar@intel.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>