mksysmap: Fix the mismatch of '.L' symbols in System.map

mksysmap: Fix the mismatch of '.L' symbols in System.map

[ Upstream commit 72d24accf02add25e08733f0ecc93cf10fcbd88c ]

When System.map was generated, the kernel used mksysmap to
filter the kernel symbols, but all the symbols with the
second letter 'L' in the kernel were filtered out, not just
the symbols starting with 'dot + L'.

For example:
ashimida@ubuntu:~/linux$ cat System.map |grep ' .L'
ashimida@ubuntu:~/linux$ nm -n vmlinux |grep ' .L'
ffff0000088028e0 t bLength_show
......
ffff0000092e0408 b PLLP_OUTC_lock
ffff0000092e0410 b PLLP_OUTA_lock

The original intent should be to filter out all local symbols
starting with '.L', so the dot should be escaped.

Fixes: 00902e984732 ("mksysmap: Add h8300 local symbol pattern")
Signed-off-by: ashimida <ashimida@linux.alibaba.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>