stm32/boards/NUCLEO_L073RZ: Skip board-pin names for CPU only pins.

This board doesn't have much flash and removing these unneeded names saves
about 900 bytes of code size.

ports/stm32/boards/NUCLEO_L073RZ/pins.csv

@@ -33,55 +33,55 @@ SWDIO,PA13
 SWCLK,PA14
 USER_B1,PC13
 LED_GREEN,PA5
-PA0,PA0
+,PA0
-PA1,PA1
+,PA1
-PA2,PA2
+,PA2
-PA3,PA3
+,PA3
-PA4,PA4
+,PA4
-PA5,PA5
+,PA5
-PA6,PA6
+,PA6
-PA7,PA7
+,PA7
-PA8,PA8
+,PA8
-PA9,PA9
+,PA9
-PA10,PA10
+,PA10
-PA11,PA11
+,PA11
-PA12,PA12
+,PA12
-PA13,PA13
+,PA13
-PA14,PA14
+,PA14
-PA15,PA15
+,PA15
-PB0,PB0
+,PB0
-PB1,PB1
+,PB1
-PB2,PB2
+,PB2
-PB3,PB3
+,PB3
-PB4,PB4
+,PB4
-PB5,PB5
+,PB5
-PB6,PB6
+,PB6
-PB7,PB7
+,PB7
-PB8,PB8
+,PB8
-PB9,PB9
+,PB9
-PB10,PB10
+,PB10
-PB11,PB11
+,PB11
-PB12,PB12
+,PB12
-PB13,PB13
+,PB13
-PB14,PB14
+,PB14
-PB15,PB15
+,PB15
-PC0,PC0
+,PC0
-PC1,PC1
+,PC1
-PC2,PC2
+,PC2
-PC3,PC3
+,PC3
-PC4,PC4
+,PC4
-PC5,PC5
+,PC5
-PC6,PC6
+,PC6
-PC7,PC7
+,PC7
-PC8,PC8
+,PC8
-PC9,PC9
+,PC9
-PC10,PC10
+,PC10
-PC11,PC11
+,PC11
-PC12,PC12
+,PC12
-PC13,PC13
+,PC13
-PC14,PC14
+,PC14
-PC15,PC15
+,PC15
-PD2,PD2
+,PD2
-PF0,PF0
+,PF0
-PF1,PF1
+,PF1
-PF11,PF11
+,PF11