clk: ti: am43x: Fix boot with CONFIG_SOC_AM33XX disabled

clk: ti: am43x: Fix boot with CONFIG_SOC_AM33XX disabled

Define ti_clk_register_dpll_x2() and of_ti_am3_dpll_x2_setup() if
AM43XX is defined.

Fixes the below boot issue.

[    2.157258] gpmc_l3_clk not enabled
[    2.161194] gpmc_l3_clk not enabled
[    2.164896] Division by zero in kernel.
[    2.169055] CPU: 0 PID: 321 Comm: kworker/u2:2 Tainted: G        W     3.16.0-rc1-00008-g4c0e520 #273
[    2.178880] Workqueue: deferwq deferred_probe_work_func
[    2.184459] [<c001477c>] (unwind_backtrace) from [<c001187c>] (show_stack+0x10/0x14)
[    2.192752] [<c001187c>] (show_stack) from [<c0530f28>] (dump_stack+0x80/0x9c)
[    2.200486] [<c0530f28>] (dump_stack) from [<c02c867c>] (Ldiv0+0x8/0x10)
[    2.207678] [<c02c867c>] (Ldiv0) from [<c0022da0>] (gpmc_calc_divider+0x24/0x40)
[    2.215490] [<c0022da0>] (gpmc_calc_divider) from [<c0022e20>] (gpmc_cs_set_timings+0x18/0x474)
[    2.224783] [<c0022e20>] (gpmc_cs_set_timings) from [<c003069c>] (gpmc_nand_init+0x74/0x1a8)
[    2.233791] [<c003069c>] (gpmc_nand_init) from [<c0024668>] (gpmc_probe+0x52c/0x874)
[    2.242089] [<c0024668>] (gpmc_probe) from [<c0349218>] (platform_drv_probe+0x18/0x48)
[    2.250534] [<c0349218>] (platform_drv_probe) from [<c0347d88>] (driver_probe_device+0x104/0x22c)
[    2.259988] [<c0347d88>] (driver_probe_device) from [<c03464dc>] (bus_for_each_drv+0x44/0x8c)
[    2.269087] [<c03464dc>] (bus_for_each_drv) from [<c0347c4c>] (device_attach+0x74/0x8c)
[    2.277620] [<c0347c4c>] (device_attach) from [<c0347380>] (bus_probe_device+0x88/0xb0)
[    2.286074] [<c0347380>] (bus_probe_device) from [<c0347768>] (deferred_probe_work_func+0x60/0x90)
[    2.295611] [<c0347768>] (deferred_probe_work_func) from [<c004ef50>] (process_one_work+0x1b4/0x4bc)
[    2.305288] [<c004ef50>] (process_one_work) from [<c004f3d4>] (worker_thread+0x148/0x550)
[    2.313954] [<c004f3d4>] (worker_thread) from [<c0055a48>] (kthread+0xc8/0xe4)
[    2.321628] [<c0055a48>] (kthread) from [<c000e648>] (ret_from_fork+0x14/0x2c)

Signed-off-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>