ring-buffer: Remove cpu_buffer argument from the rb_inc_page()

The cpu_buffer argument is not used inside the rb_inc_page() after
commit 3adc54fa ("ring-buffer: make the buffer a true circular link
list").
And cpu_buffer argument is not used inside the two functions too,
rb_is_head_page/rb_set_list_to_head.

Link: https://lkml.kernel.org/r/20201225140356.23008-1-hqjagain@gmail.com



Signed-off-by: Qiujun Huang <hqjagain@gmail.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>