selftests: tpm2: create a dedicated .gitignore

selftests: tpm2: create a dedicated .gitignore

The tpm2 selftests produce two logs: SpaceTest.log and
AsyncTest.log. Only SpaceTest.log was listed in selftests/.gitignore,
while AsyncTest.log remained untracked.

This change creates a dedicated .gitignore in the tpm2/ directory to
manage these entries, keeping tpm2-specific patterns isolated from
parent .gitignore.

Fixed white-space errors during commit
Shuah Khan <skhan@linuxfoundation.org>

Link: https://lore.kernel.org/r/20250126195147.902608-1-khaledelnaggarlinux@gmail.com
Signed-off-by: Khaled Elnaggar <khaledelnaggarlinux@gmail.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>