lpc32xx: add support for board work_92105

Work_92105 from Work Microwave is an LPC3250-
based board with the following features:
- 64MB or 128MB SDR DRAM
- 1 GB SLC NAND, managed through MLC controller.
- Ethernet
- Ethernet + PHY SMSC8710
- I2C:
  - EEPROM (24M01-compatible)
  - RTC (DS1374-compatible)
  - Temperature sensor (DS620)
  - DACs (2 x MAX518)
- SPI (through SSP interface)
  - Port expander MAX6957
- LCD display (HD44780-compatible), controlled
  through the port expander and DACs

This board has SPL support, and uses the LPC32XX boot
image format.

Signed-off-by: Albert ARIBAUD (3ADEV) <albert.aribaud@3adev.fr>