driver: ethernet: stmmac: remove the redundant clock disable action

When run below command to remove ethernet driver on
stratix10 platform, there will be warning trace as below:

$ cd /sys/class/net/etha01/device/driver
$ echo ff800000.ethernet > unbind

WARNING: CPU: 3 PID: 386 at drivers/clk/clk.c:810 clk_core_unprepare+0x114/0x274
Modules linked in: sch_fq_codel
CPU: 3 PID: 386 Comm: sh Tainted: G        W         5.10.74-yocto-standard #1
Hardware name: SoCFPGA Stratix 10 SoCDK (DT)
pstate: 00000005 (nzcv daif -PAN -UAO -TCO BTYPE=--)
pc : clk_core_unprepare+0x114/0x274
lr : clk_core_unprepare+0x114/0x274
sp : ffff800011bdbb10
clk_core_unprepare+0x114/0x274
 clk_unprepare+0x38/0x50
 stmmac_remove_config_dt+0x40/0x80
 stmmac_pltfr_remove+0x64/0x80
 platform_drv_remove+0x38/0x60
 ... ..
 el0_sync_handler+0x1a4/0x1b0
 el0_sync+0x180/0x1c0
This issue is introduced by upstream commit 8f269102


("net: stmmac: disable clocks in stmmac_remove_config_dt()")
Because clock has been disabled in function stmmac_dvr_remove()
It not reasonable the remove clock disable action from function
stmmac_remove_config_dt(), because it is mainly used in probe failed,
and other platform drivers also use this common function. So, remove
stmmac_remove_config_dt() from stmmac_pltfr_remove(), only other
necessary code.

Signed-off-by: Meng Li <Meng.Li@windriver.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
Signed-off-by: Liwei Song <liwei.song@windriver.com>