ARM: uniphier: move sg_set_{pinsel, iectrl} to more relevant places

Move the sg_set_pinsel macro to arch/arm/mach-uniphier/arm32/debug_ll.S
since it is not used anywhere else.

Move the C functions sg_set_{pinsel,iectrl} to debug-uart.c since they
are not used anywhere else.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>