uboot-imx

am33xx: Rework #ifdef's around s_init for clarity

The s_init function is only called on SPL or XIP cases, so lets only
build it for them.  This makes the #if logic within the function a bit
clearer as to when we are or are not calling things, and makes it easier
to see that for example preloader_console_init isn't ever called in the
non-XIP full U-Boot case.

Signed-off-by: Tom Rini <trini@ti.com>