staging: rtl8723au: Fix static symbol sparse warning

Fix sparse warning:
drivers/staging/rtl8723au/core/rtw_efuse.c:579:5: warning: symbol 'efuse_GetCurrentSize23a' was not declared. Should it be static?
by removing efuse_GetCurrentSize23a since its never used

Signed-off-by: Miguel Oliveira <cmroliv@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>