Fix only PWM 0 being enabled via Pinmux

Currently, all the PWMs (minus the LCD backlight) are being routed
through pinmux, but the value being passed for the PWM output
enable is the constant `'{'b1}'`. Because the inner value is `'b1`,
this is extended to fill the 7 bit PWM output range as `000001`,
instead of using `'1` which would extend to `111111`.

This commit makes the casting/extension of these constant enable
values more explicitly match the PWM output size and module count, to
ensure that all outputs of all PWM devices are being enabled through
pinmux.

rtl/system/sonata_system.sv

@@ -1208,8 +1208,8 @@ module sonata_system
     .clk_i(clk_sys_i),
     .rst_ni(rst_sys_ni),
 
-    .pwm_out_i('{pwm_modulated}),
-    .pwm_out_en_i('{'b1}),
+    .pwm_out_i('{PWM_NUM{pwm_modulated}}),
+    .pwm_out_en_i('{PWM_NUM{{PWM_OUT_WIDTH{1'b1}}}}),
 
     .uart_rx_o(uart_rx),
     .uart_tx_i(uart_tx),