realtek: Remove extern from function declarations

realtek: Remove extern from function declarations

In contrast to variables, functions don't need extern declarations. It is
also preferred in the kernel not to use extern in front of function
declarations.

The extern+static parts in clk-rtl83xx.c were skipped because they are a
little bit unexpected ("extern *_dram_set_rate" are never used, "static
_sram_set_rate" are used but should from the C code perspective always be
NULL). This is left for an interested reader with the correct test HW and
some interests to dig in the code from commit 4850bd887c3a ("realtek: add
RTL83XX clock driver") for the *_dram_set_rate -> *_sram_set_rate
relocation and how these SRAM function pointers are set in this translation
unit.

Signed-off-by: Sven Eckelmann <[email protected]>
Link: https://github.com/openwrt/openwrt/pull/20906
Signed-off-by: Hauke Mehrtens <[email protected]>