QCLINUX: qcom.config: Enable 39-bit VA space for 4K-page builds

For Qualcomm 4K-page based builds, explicitly enable VA_BITS_39
in the qcom.config fragment.

Lower-end arm64 systems typically do not benefit from a 48/52-bit VA
space, while they do benefit from smaller page tables and reduced TLB
pressure.

Selecting 39-bit VA sizing aligns better with constraints and performance
characteristics of lower-end Qualcomm platforms.

This change does not affect 64K-page builds (which retain 48/52-bit VA).

Background:
- With 4K pages, arm64 supports 39-bit (3-level) or 48-bit (4-level) VAs.
- 52-bit VAs are only available with 64K pages and ARMv8.2-LVA, and
  kernels must be able to fall back to 48-bit at boot.

Signed-off-by: Anurag Pateriya <[email protected]>

Author: apateriy-qcom

arch/arm64/configs/qcom.config

@@ -4,6 +4,7 @@
 #
 # Keep alphabetically sorted
 CONFIG_ARM64_SW_TTBR0_PAN=y
+CONFIG_ARM64_VA_BITS_39=y
 CONFIG_ATH_REG_DYNAMIC_USER_REG_HINTS=y
 CONFIG_BT_BNEP=m
 CONFIG_BT_BNEP_MC_FILTER=y