ACPI: Move sleep code from system.c to sleep.c

struct acpi_system was removed, because it was an unncessary abstraction (a single array suffices).
All functions have been updated to reference the array. 

Unnecessary headers were removed, including ones implicitly included.

procfs files controlling sleep support were moved. 

sysrq handler and registration were removed. 

acpi_sleep_init() made an implicit subsys_initcall.

drivers/acpi/Makefile

@@ -43,6 +43,7 @@ obj-$(CONFIG_ACPI_POWER)	+= power.o
 obj-$(CONFIG_ACPI_PROCESSOR)	+= processor.o
 obj-$(CONFIG_ACPI_THERMAL)	+= thermal.o
 obj-$(CONFIG_ACPI_SYSTEM)	+= system.o
+obj-$(CONFIG_ACPI_SLEEP)	+= sleep.o
 obj-$(CONFIG_ACPI_NUMA)		+= numa.o
 obj-$(CONFIG_ACPI_TOSHIBA)	+= toshiba_acpi.o