ppc4xx_sdram: Get rid of the init RAM hack

ppc4xx_sdram: Get rid of the init RAM hack

The do_init parameter of ppc4xx_sdram_init() is used to map memory
regions that is normally done by the firmware by programming the SDRAM
controller. Do this from board code emulating what firmware would do
when booting a kernel directly from -kernel without a firmware so we
can get rid of this do_init hack.

Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Message-Id: <d6c44c870befa1a075e21f1a59926dcdaff63f6b.1664021647.git.balaton@eik.bme.hu>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>