HID: Intel-thc-hid: Intel-quicki2c: Use size_t for all length variables

HID: Intel-thc-hid: Intel-quicki2c: Use size_t for all length variables

Convert all length-related variables in the QuickI2C protocol layer to use
size_t type to follow kernel coding conventions.

This includes:
- All buffer length parameters and variables
- Return values of quicki2c_encode_cmd() function which represents
  encoded command buffer size.
- Return values of quicki2c_init_write_buf() function which represents
  process result: either prepared output buffer size or error code.

This change improves type consistency and aligns with standard kernel
practices for memory size representation, reducing potential issues
with size calculations and comparisons.

Signed-off-by: Even Xu <even.xu@intel.com>
Signed-off-by: Jiri Kosina <jkosina@suse.com>