ACPI: TAD: Add missing sysfs_remove_group() for ACPI_TAD_RT

ACPI: TAD: Add missing sysfs_remove_group() for ACPI_TAD_RT

Previously, after `rmmod acpi_tad`, `modprobe acpi_tad` would fail
with this dmesg:

sysfs: cannot create duplicate filename '/devices/platform/ACPI000E:00/time'
Call Trace:
 <TASK>
 dump_stack_lvl+0x6c/0x90
 dump_stack+0x10/0x20
 sysfs_warn_dup+0x8b/0xa0
 sysfs_add_file_mode_ns+0x122/0x130
 internal_create_group+0x1dd/0x4c0
 sysfs_create_group+0x13/0x20
 acpi_tad_probe+0x147/0x1f0 [acpi_tad]
 platform_probe+0x42/0xb0
 </TASK>
acpi-tad ACPI000E:00: probe with driver acpi-tad failed with error -17

Fixes: 3230b2b3c1ab ("ACPI: TAD: Add low-level support for real time capability")
Signed-off-by: Daniel Tang <danielzgtg.opensource@gmail.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Link: https://patch.msgid.link/2881298.hMirdbgypa@daniel-desktop3
Cc: 5.2+ <stable@vger.kernel.org> # 5.2+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>