ppc4xx_sdram: Rename functions to prevent name clashes

ppc4xx_sdram: Rename functions to prevent name clashes

Rename functions to avoid name clashes when moving the DDR2 controller
model currently called ppc440_sdram to ppc4xx_devs. This also more
clearly shows which function belongs to which model.

Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <9c09d10fbf36940ebbe30d7038d69cf3f2e58371.1664021647.git.balaton@eik.bme.hu>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>