selftests/arm64: Fix MTE prctl TAP plan

selftests/arm64: Fix MTE prctl TAP plan

The MTE prctl test emits one result from check_basic_read() followed by
one result for each of the seven entries in mte_modes[]. However, the TAP
plan only accounts for the array entries, producing:

  # Planned tests != run tests (7 != 8)

Include the basic read check in the plan so that all eight emitted results
are declared.

Reviewed-by: Mark Brown <broonie@kernel.org>
Fixes: 1f488fb91378 ("kselftest/arm64/mte: Add MTE_STORE_ONLY testcases")
Signed-off-by: Muhammad Usama Anjum <usama.anjum@arm.com>
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>