powerpc/time: Define div128_by_32() static and __init

powerpc/time: Define div128_by_32() static and __init

div128_by_32() used to be called from outside time.c in the old days
but since v2.6.15 it hasn't been used outside time.c

$ git grep div128_by_32 v2.6.14
v2.6.14:arch/ppc64/kernel/iSeries_setup.c:	div128_by_32(1024 * 1024, 0, tb_ticks_per_sec, &divres);
v2.6.14:arch/ppc64/kernel/pmac_time.c:	div128_by_32( 1024*1024, 0, tb_ticks_per_sec, &divres );
v2.6.14:arch/ppc64/kernel/time.c:				div128_by_32( XSEC_PER_SEC, 0, tb_ticks_per_sec, &divres );
v2.6.14:arch/ppc64/kernel/time.c:	div128_by_32(1024*1024, 0, tb_ticks_per_sec, &divres);
v2.6.14:arch/ppc64/kernel/time.c:	div128_by_32(1000000000, 0, tb_ticks_per_sec, &res);
v2.6.14:arch/ppc64/kernel/time.c:	div128_by_32( 1024*1024, 0, new_tb_ticks_per_sec, &divres );
v2.6.14:arch/ppc64/kernel/time.c:void div128_by_32( unsigned long dividend_high, unsigned long dividend_low,
v2.6.14:include/asm-ppc64/time.h:void div128_by_32( unsigned long dividend_high, unsigned long dividend_low,

$ git grep div128_by_32 v2.6.15
v2.6.15:arch/powerpc/kernel/time.c:				div128_by_32( XSEC_PER_SEC, 0, tb_ticks_per_sec, &divres );
v2.6.15:arch/powerpc/kernel/time.c:	div128_by_32(1024*1024, 0, tb_ticks_per_sec, &res);
v2.6.15:arch/powerpc/kernel/time.c:	div128_by_32(1000000000, 0, tb_ticks_per_sec, &res);
v2.6.15:arch/powerpc/kernel/time.c:	div128_by_32(1024*1024, 0, new_tb_ticks_per_sec, &divres);
v2.6.15:arch/powerpc/kernel/time.c:void div128_by_32(u64 dividend_high, u64 dividend_low,
v2.6.15:include/asm-powerpc/time.h:extern void div128_by_32(u64 dividend_high, u64 dividend_low,

Move it above its only caller which is time_init() and define it
static and __init.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/50810349bf1eee378fbeab72a36e4b6553a60c3d.1738749246.git.christophe.leroy@csgroup.eu