spl: Remove inline ifdef check for EXT and FAT support

These files are only included for build by the make system
when CONFIG_SPL_{EXT,FAT}_SUPPORT is enabled, remove the unneed
checks for these in the source files.

Signed-off-by: Andrew F. Davis <afd@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>