ARM: common: edma: edma_pm_resume may be unused

The recently introduced resume hook in the edma driver
is not referenced when CONFIG_PM_SLEEP is not set, which
results in a compile warning in keystone builds.

This adds an appropriate #ifdef.

Cc: Nishanth Menon <nm@ti.com>
Cc: Daniel Mack <zonque@gmail.com>
Cc: Joel Fernandes <joelf@ti.com>
Acked-by: Sekhar Nori <nsekhar@ti.com>
Fixes: a2b1175131: ("ARM: common: edma: add suspend resume hook")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>