arm64: Remove __exception_text_start and __exception_text_end from asm/section.h

Linux commit b6e43c0e ("arm64: remove __exception annotations") has
removed __exception_text_start and __exception_text_end sections.

So removing reference of __exception_text_start and __exception_text_end
from from asm/section.h.

Cc: James Morse <james.morse@arm.com>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Signed-off-by: Prabhakar Kushwaha <pkushwaha@marvell.com>
Signed-off-by: Will Deacon <will@kernel.org>

arch/arm64/include/asm/sections.h

@@ -8,7 +8,6 @@
 #include <asm-generic/sections.h>
 
 extern char __alt_instructions[], __alt_instructions_end[];
-extern char __exception_text_start[], __exception_text_end[];
 extern char __hibernate_exit_text_start[], __hibernate_exit_text_end[];
 extern char __hyp_idmap_text_start[], __hyp_idmap_text_end[];
 extern char __hyp_text_start[], __hyp_text_end[];