ARM: imx: common: Move prototype outside the SMP block

Currently the imx_gpcv2_set_core1_pdn_pup_by_software() prototype is
guarded by the CONFIG_SMP symbol. This causes W=1 build warnings when
CONFIG_SMP is not selected:

arch/arm/mach-imx/src.c:103:6: warning: no previous prototype for 'imx_gpcv2_set_core1_pdn_pup_by_software' [-Wmissing-prototypes]

Fix it by moving the imx_gpcv2_set_core1_pdn_pup_by_software() prototype
outside of the CONFIG_SMP block.

Fixes: e34645f4

 ("ARM: imx: add smp support for imx7d")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Fabio Estevam <festevam@denx.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>