platform/x86: thinkpad_acpi: Fix errors reading battery thresholds

platform/x86: thinkpad_acpi: Fix errors reading battery thresholds

Check whether the battery supports the relevant charge threshold before
reading the value to silence these errors:

thinkpad_acpi: acpi_evalf(BCTG, dd, ...) failed: AE_NOT_FOUND
ACPI: \_SB_.PCI0.LPC_.EC__.HKEY: BCTG: evaluate failed
thinkpad_acpi: acpi_evalf(BCSG, dd, ...) failed: AE_NOT_FOUND
ACPI: \_SB_.PCI0.LPC_.EC__.HKEY: BCSG: evaluate failed

when reading the charge thresholds via sysfs on platforms that do not
support them such as the ThinkPad T400.

Fixes: 2801b9683f74 ("thinkpad_acpi: Add support for battery thresholds")
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=202619
Signed-off-by: Jonathan Teh <jonathan.teh@outlook.com>
Reviewed-by: Mark Pearson <mpearson-lenovo@squebb.ca>
Link: https://patch.msgid.link/MI0P293MB01967B206E1CA6F337EBFB12926CA@MI0P293MB0196.ITAP293.PROD.OUTLOOK.COM
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>