soc: intel_adsp: ace: Update power_down to use new HPSRAM power-down macro

Refactor the power_down function to utilize the newly introduced
m_ace_hpsram_power_down_entire macro for shutting down the entire
HPSRAM. This change simplifies the power-down process by replacing the
previous segment-based power gating mask approach with a single boolean
flag that indicates whether the entire HPSRAM should be disabled.

The function signature of power_down has been updated to accept the new
boolean flag, and the corresponding call sites have been modified to
pass the flag based on the CONFIG_ADSP_POWER_DOWN_HPSRAM Kconfig option.

Additionally, the assembly code has been cleaned up to remove the
now-obsolete hpsram_mask array and related logic.

Signed-off-by: Tomasz Leman <tomasz.m.leman@intel.com>