tracing: Drop unneeded assignment in ring_buffer_resize()

Since commit 0a1754b2 ("ring-buffer: Return 0 on success from
ring_buffer_resize()"), computing the size is not needed anymore.

Drop unneeded assignment in ring_buffer_resize().

Link: https://lkml.kernel.org/r/20201214084503.3079-1-lukas.bulwahn@gmail.com



Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>