remove all references to .dynsym

remove all references to .dynsym

Discard all .dynsym sections from linker scripts
Remove all __dynsym_start definitions from linker scripts
Remove all __dynsym_start references from the codebase

Note: this touches include/asm-generic/sections.h, which
is not ARM-specific, but actual uses of __dynsym_start
are only in ARM, so this patch can safely go through
the ARM repository.

Signed-off-by: Albert ARIBAUD <[email protected]>
Tested-by: Lubomir Popov <[email protected]>
Tested-by: Jeroen Hofstee <[email protected]>
Reviewed-by: Benoît Thébaudeau <[email protected]>