Documentation: x86: Fix obsolete name of page fault handler

Documentation: x86: Fix obsolete name of page fault handler

Since commit 74346978a683 ("x86/entry: Switch page fault exception to
IDTENTRY_RAW"), the function name of the page fault handler is out of date.
And because of commit 9ee67d87c8c0 ("x86/mm: Break out user address space
handling"), the description of search_exception_table is not correct
anymore. It may mislead the user who wants to use the documentation to
figure out the page fault handler.

Also, fix typo and add the parentheses after function and macro name.

Signed-off-by: Chin En Lin <shiyn.lin@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>