ARM: nspire: Fix compiler warning

CC      arch/arm/mach-nspire/nspire.o
arch/arm/mach-nspire/nspire.c:79:2: warning: initialization from incompatible pointer type [enabled by default]
arch/arm/mach-nspire/nspire.c:79:2: warning: (near initialization for '__mach_desc_NSPIRE.restart') [enabled by default]

Signed-off-by: Alexander Shiyan <shc_work@mail.ru>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>