tpm/eventlog: remove redundant assignment to variabel ret

Variable ret is being assigned and error code that is never read, it is
either being re-assigned in an error exit path or never referenced again
on the non-error path. The assignment is redundant and can be removed.

Cleans up clang scan build warning:
drivers/char/tpm/eventlog/acpi.c:145:2: warning: Value stored to 'ret'
is never read [deadcode.DeadStores]

Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>