selftests/sgx: Fix linker script asserts

selftests/sgx: Fix linker script asserts

[ Upstream commit 9fd552ee32c6c1e27c125016b87d295bea6faea7 ]

DEFINED only considers symbols, not section names. Hence, replace the
check for .got.plt with the _GLOBAL_OFFSET_TABLE_ symbol and remove other
(non-essential) asserts.

Signed-off-by: Jo Van Bulck <jo.vanbulck@cs.kuleuven.be>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Link: https://lore.kernel.org/all/20231005153854.25566-10-jo.vanbulck%40cs.kuleuven.be
Signed-off-by: Sasha Levin <sashal@kernel.org>