extcon: palmas: Fix NULL pointer error

This patch fixes NULL pointer error by removing the unneeded kfree() call
of edev->name because extcon-palmas no longer allocate the memory for edev->name.

Fixes: d71aadda ("extcon: Remove the optional name of extcon device")
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>