ARM: SoCFPGA: Fix secondary CPU startup in thumb2 kernel

The secondary CPU starts up in ARM mode. When the kernel is compiled in
thumb2 mode we have to explicitly compile the secondary startup
trampoline in ARM mode, otherwise the CPU will go to Nirvana.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Reported-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
Suggested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: stable@vger.kernel.org
Signed-off-by: Dinh Nguyen <dinguyen@opensource.altera.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>