Documentation: i2c: fix references to other documents

Similar to commit fe99b819 ("docs: i2c: i2c-sysfs: fix hyperlinks"),
make other links in documentation consistent with the preferred way.
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Tested-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

Documentation/i2c/dev-interface.rst

@@ -148,7 +148,7 @@ You can do plain I2C transactions by using read(2) and write(2) calls.
 You do not need to pass the address byte; instead, set it through
 ioctl I2C_SLAVE before you try to access the device.
 
-You can do SMBus level transactions (see documentation file smbus-protocol
+You can do SMBus level transactions (see documentation file smbus-protocol.rst
 for details) through the following functions::
 
   __s32 i2c_smbus_write_quick(int file, __u8 value);

Documentation/i2c/slave-interface.rst

@@ -32,9 +32,9 @@ User manual
 ===========
 
 I2C slave backends behave like standard I2C clients. So, you can instantiate
-them as described in the document 'instantiating-devices'. The only difference
-is that i2c slave backends have their own address space. So, you have to add
-0x1000 to the address you would originally request. An example for
+them as described in the document instantiating-devices.rst. The only
+difference is that i2c slave backends have their own address space. So, you
+have to add 0x1000 to the address you would originally request. An example for
 instantiating the slave-eeprom driver from userspace at the 7 bit address 0x64
 on bus 1::
 

Documentation/i2c/writing-clients.rst

@@ -364,7 +364,7 @@ stop condition is issued between transaction. The i2c_msg structure
 contains for each message the client address, the number of bytes of the
 message and the message data itself.
 
-You can read the file ``i2c-protocol`` for more information about the
+You can read the file i2c-protocol.rst for more information about the
 actual I2C protocol.
 
 
@@ -414,7 +414,7 @@ transactions return 0 on success; the 'read' transactions return the read
 value, except for block transactions, which return the number of values
 read. The block buffers need not be longer than 32 bytes.
 
-You can read the file ``smbus-protocol`` for more information about the
+You can read the file smbus-protocol.rst for more information about the
 actual SMBus protocol.