USB: ehci-spear: add CONFIG_PM_SLEEP to suspend/resume functions

Add CONFIG_PM_SLEEP to suspend/resume functions to fix the following
build warning when CONFIG_PM_SLEEP is not selected. This is because
sleep PM callbacks defined by SIMPLE_DEV_PM_OPS are only used when
the CONFIG_PM_SLEEP is enabled.

drivers/usb/host/ehci-spear.c:82:12: warning: 'ehci_spear_drv_suspend' defined but not used [-Wunused-function]
drivers/usb/host/ehci-spear.c:90:12: warning: 'ehci_spear_drv_resume' defined but not used [-Wunused-function]

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>