ARM: at91: cleanup initilisation code by removing dead code

The AT91-specific SoC strucutre "struct at91_init_soc" was filled with specific
!DT initilisation functions. Now that we got rid of the !DT board file
description, remove unneeded functions.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
[nicolas.ferre@atmel.com: split patch]
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>