staging: rtl8188eu: make efuse_power_switch() function static

The `rtl8188eu` driver is built as a kmod in order to avoid symbol
conflicts (at link-time) with other Realtek drivers.

Internally, we use this driver as builtin [vs kmod], and we've identified
the `efuse_power_switch()` symbol to be conflicting at link-time with the
one from the `rtlwifi` driver.

An alternative solution would have been to rename the function, but it
doesn't look like it's being used outside of this driver, so just make it
static.
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Link: https://lore.kernel.org/r/20191016065834.12186-1-alexandru.ardelean@analog.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8188eu/core/rtw_efuse.c

@@ -25,7 +25,7 @@ enum{
  * When we want to enable write operation, we should change to pwr on state.
  * When we stop write, we should switch to 500k mode and disable LDO 2.5V.
  */
-void efuse_power_switch(struct adapter *pAdapter, u8 write, u8 pwrstate)
+static void efuse_power_switch(struct adapter *pAdapter, u8 write, u8 pwrstate)
 {
 	u8 tempval;
 	u16 tmpv16;

drivers/staging/rtl8188eu/include/rtw_efuse.h

@@ -82,7 +82,6 @@ u8 efuse_OneByteWrite(struct adapter *adapter, u16 addr, u8 data);
 
 void efuse_ReadEFuse(struct adapter *Adapter, u8 efuseType, u16 _offset,
 		u16 _size_byte, u8 *pbuf);
-void efuse_power_switch(struct adapter *adapt, u8 write, u8  pwrstate);
 int Efuse_PgPacketRead(struct adapter *adapt, u8 offset, u8 *data);
 bool Efuse_PgPacketWrite(struct adapter *adapter, u8 offset, u8 word, u8 *data);
 void efuse_WordEnableDataRead(u8 word_en, u8 *sourdata, u8 *targetdata);