hexagon: use common DISCARDS macro

ld.lld warns that the '.modinfo' section is not currently handled:

ld.lld: warning: kernel/built-in.a(workqueue.o):(.modinfo) is being placed in '.modinfo'
ld.lld: warning: kernel/built-in.a(printk/printk.o):(.modinfo) is being placed in '.modinfo'
ld.lld: warning: kernel/built-in.a(irq/spurious.o):(.modinfo) is being placed in '.modinfo'
ld.lld: warning: kernel/built-in.a(rcu/update.o):(.modinfo) is being placed in '.modinfo'

The '.modinfo' section was added in commit 898490c0 ("moduleparam:
Save information about built-in modules in separate file") to the DISCARDS
macro but Hexagon has never used that macro.  The unification of DISCARDS
happened in commit 023bf6f1 ("linker script: unify usage of discard
definition") in 2009, prior to Hexagon being added in 2011.

Switch Hexagon over to the DISCARDS macro so that anything that is
expected to be discarded gets discarded.

Link: https://lkml.kernel.org/r/20210521011239.1332345-3-nathan@kernel.org
Fixes: e95bf452

 ("Hexagon: Add configuration and makefiles for the Hexagon architecture.")
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Brian Cain <bcain@codeaurora.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Oliver Glitta <glittao@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>