clk: thead: Add CLK_IGNORE_UNUSED to fix TH1520 boot

clk: thead: Add CLK_IGNORE_UNUSED to fix TH1520 boot

Add the CLK_IGNORE_UNUSED flag to apb_pclk, cpu2peri_x2h_clk,
perisys_apb2_hclk and perisys_apb3_hclk.

Without this flag, the boot hangs after "clk: Disabling unused clocks"
unless clk_ignore_unused is in the kernel cmdline.

Fixes: ae81b69fd2b1 ("clk: thead: Add support for T-Head TH1520 AP_SUBSYS clocks")
Signed-off-by: Drew Fustini <dfustini@tenstorrent.com>
Link: https://lore.kernel.org/r/20250113-th1520-clk_ignore_unused-v1-2-0b08fb813438@tenstorrent.com
Signed-off-by: Stephen Boyd <sboyd@kernel.org>