esoc: Move the esoc client hooks' definitions from uapi header

The definitions under 'enum esoc_client_hook_prio' and 'struct
esoc_link_data' are used only by kernel drivers, and not needed
by user-space. Hence, move the definitions from uapi header file
(uapi/linux/esoc_ctrl.h) to kernel internal header file
(linux/esoc_client.h).

Change-Id: I74b4f470ff61518fa2df2e872595b5e8e6e4c307
Signed-off-by: Raghavendra Rao Ananta <rananta@codeaurora.org>