ARM: avoid ARM binutils leaking ELF local symbols

Symbols starting with .L are ELF local symbols and should not appear
in ELF symbol tables.  However, unfortunately ARM binutils leaks the
.LANCHOR symbols into the symbol table, which leads kallsyms to report
these symbols rather than the real name.  It is not very useful when
%pf reports symbols against these leaked .LANCHOR symbols.

Arrange for kallsyms to ignore these symbols using the same mechanism
that is used for the ARM mapping symbols.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>