soc: imx: imx93-blk-ctrl: Add dedicated lockdep class for nested genpd locks

This is the same approach as being used within imx8mp-blk-ctrl. This fixes
the lockdep warning about 'possible recursive locking detected' with the
following (reduced) backtrace:
genpd_lock_mtx+0x14/0x1c
genpd_runtime_resume+0x108/0x308
__rpm_callback+0x44/0x19c
rpm_callback+0x64/0x70
rpm_resume+0x438/0x6d8
__pm_runtime_resume+0x54/0xb0
imx93_blk_ctrl_power_on+0x100/0x294
_genpd_power_on+0x8c/0x16c
genpd_power_on.part.0+0xa0/0x1a0
__genpd_dev_pm_attach+0x14c/0x2e4
genpd_dev_pm_attach+0x58/0x64
dev_pm_domain_attach+0x1c/0x2c

Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>