clk: hi3516dv300: add GPL license info.

driver inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I65S6L



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Building with allmoddefconfig will display the warning message as follows:
"WARNING: modpost: missing MODULE_LICENSE() in drivers/clk/hisilicon/clk-hi3516dv300.o"

This patch will fix this issue by adding GPL license.

Signed-off-by: taolan <taolan@huawei.com>