arm: socfpga: Clean up SoCFPGA configuration

Reorganize and cleanup the configuration file for SoCFPGA. There
is no functional change after this cleanup. This was necessary,
since the file was a wild mess and it was impossible to make sense
of it's content, let alone change something without breaking some
other thing. This patch puts the contents on par with regular U-Boot
standards.

Also remove unused preprocessor symbols CONFIG_SINGLE_BOOTOADER
and CONFIG_USE_IRQ, which is undefined by default. Finally, do
logical reordering of the defines in the file so it's much more
readable. The reordering was also necessary for the splitting
as the initial one was messy.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Chin Liang See <clsee@altera.com>
Cc: Dinh Nguyen <dinguyen@altera.com>
Cc: Albert Aribaud <albert.u.boot@aribaud.net>
Cc: Tom Rini <trini@ti.com>
Cc: Wolfgang Denk <wd@denx.de>
Cc: Pavel Machek <pavel@denx.de>