spi_flash: remove duplicate definition of spi_flash_unlock

The other (static) definition is in flash_ops.c, all references are
also in flash_ops.c.

components/spi_flash/esp_flash_api.c

@@ -646,10 +646,4 @@ esp_err_t spi_flash_read(size_t src, void *dstv, size_t size)
     return spi_flash_translate_rc(err);
 }
 
-esp_err_t spi_flash_unlock()
-{
-    esp_err_t err = esp_flash_set_chip_write_protect(NULL, false);
-    return spi_flash_translate_rc(err);
-}
-
 #endif // CONFIG_SPI_FLASH_USE_LEGACY_IMPL

components/spi_flash/flash_ops.c

@@ -198,7 +198,7 @@ static esp_rom_spiflash_result_t IRAM_ATTR spi_flash_unlock()
     }
     return ESP_ROM_SPIFLASH_RESULT_OK;
 }
-#endif
+#endif // CONFIG_SPI_FLASH_USE_LEGACY_IMPL
 
 esp_err_t IRAM_ATTR spi_flash_erase_sector(size_t sec)
 {
@@ -419,7 +419,7 @@ out:
 
     return spi_flash_translate_rc(rc);
 }
-#endif
+#endif // CONFIG_SPI_FLASH_USE_LEGACY_IMPL
 
 esp_err_t IRAM_ATTR spi_flash_write_encrypted(size_t dest_addr, const void *src, size_t size)
 {