* The Boot ROM bootloader loads only the first 32KBytes of U-Boot image
from the external 16-bit NOR flash. We make U-Boot load the remaining
contents of the image.
 * Put all function and data used for bootstrapping in the beginning
of the U-Boot image in sections `.lpc18xx_image_top_text` and
`.lpc18xx_image_top_data`.
 * Configure the boot pins to determine the boot source if the relevant
fields in the One-Time Programmable memory are not set.
 * Configure the remaining EMC pins before reading the whole U-Boot
image. The Boot ROM bootloader forgets to configure some EMC pins.
 * Reload the U-Boot image from NOR flash only when boot source is
`EMC 16-bit`.