pstore/ramoops: Fix typo as there is no "reserver"

For some reason my finger always hits the 'r' after typing "reserve".
Fix the typo in the Documentation example.

Fixes: d9d814ee ("pstore/ramoops: Add ramoops.mem_name= command line option")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Link: https://lore.kernel.org/r/20240807170029.3c1ff651@gandalf.local.home


Signed-off-by: Kees Cook <kees@kernel.org>