drm/xe/hwmon: Remove type casting

drm/xe/hwmon: Remove type casting

Refactor: eliminate type casts by using proper u32
declarations.

v2:
- Address review comments. (Karthik)

v3:
- Use the proper u32 type and drop cast. (Lucas De Marchi)
- Modify variable when actually using u64 value.
- Change r value to reg_value with u32 type.

v4:
- Remove newline between trailer and Signed-off-by. (Lucas De Marchi)
- Change reg_val to val for more user-friendly logging.
- Use mul_u32_u32 function since both values are u32.

v5:
- mul_u32_u32 function with shift. (Lucas De Marchi)

Fixes: 7596d839f6228 ("drm/xe/hwmon: Add support to manage power limits though mailbox")
Signed-off-by: Mallesh Koujalagi <mallesh.koujalagi@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://lore.kernel.org/r/20250912113458.2815172-1-mallesh.koujalagi@intel.com
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>